As a result of the accident in which he gained his powers, the Molecule Man has a series of jagged scars radiating from the bridge of his nose in a lightning-like pattern. He can use his powers to conceal the scars at will.
Owen Reece, a native of Brooklyn, New York, was a small and frail child who was raised by a coddling and over protective mother.  By his own accounts Owen has claimed contrary to this, stating that his mother gave birth to him late in life and despised him.  He has also stated that he was picked on in high school.  While growing up, Owen developed a love for magicians and aspired to be one, but this childhood dream did not come to pass.  As an adult he ended up working for the ACME Atomics Corporation and worked there for the next twelve years. Living a life beneath everyone's notice, Reece hoped for the day when he would be recognized by his peers for his hard work. While attempting to fix an atomic powered device when a trillion-to-one accident occurred bombarding him with radiation and transforming his body.  The accident also caused a "pin prick" hole between Earth's dimension and another. Allowing the being who would eventually become known as the Beyonder to become aware of a universe teeming with life, an event that would have an impact of Owen's life many years later.  Soon Reece found that he could control the molecular structure of nearly anything. When he was fired from his job due to the accident, Reece decided to use his powers to take over the world. He then dubbed himself the Molecule Man and plotted to take over New York City.  Due to his psychological problems and low self-esteem, stemming from his mother, Owen subconsciously placed limitations on his powers, such as being incapable of affecting the molecules of living things. Initially he also had to use a "magic wand" to focus his powers as well.  Owen has stated that the wand was initially used due to his past infatuation with magicians. 
Sensing the danger that the Molecule Man posed, Uatu the Watcher contacted the Fantastic Four and warned them of the threat, transporting them to face their foe as he threatened the city of New York from Time Square. The Fantastic Four initially were unable to match the powers of the Molecule Man. However their leader Mr. Fantastic was able to deduce that the Molecule Man could not alter the molecules of living things. Seeking refuge at the home of their ally, the blind sculptress Alicia Masters, the Fantastic Four had themselves covered in a thin layer of plaster and posed as statues while Alicia signaled the Molecule Man to her home. Thinking the FF were really statues made by Alicia, the Molecule Man attempted to use his powers to use the "statues" as weapons. However he soon realized his error and was ambushed by the Four. When Reed Richards confiscated the Molecule Man's wand, the Watcher swooped in and contained him, telling the Four that their foe would never menace Earth again. 
Son of Molecule Man
The Watcher placed the Molecule Man in another dimension where time moved much more rapidly hoping that the Molecule Man would die of old age. Some records indicate that the Watcher was able to reinforce the mental blocks on Owne's powers, however other sources refute this. Whatever the case, Owen apparently used his powers to create a "son" and a new wand. Already grown too old to get his revenge, Owen constructed a device that would allow his "son" to recreate the accident that gave the Molecule Man his powers. Unknown to the "son" the consciousness of the Molecule Man had been transported into the wand that channeled his powers after the original Molecule Man had died.  This iteration of the Molecule Man no longer had the limitations of his predecessor. However when attempting to use his powers to transport himself to New York City, he appeared in the Florida Everglades in the Nexus of All Realities near the town of Citrusville. He appeared before the defender of the Nexus, the muck-monster known as the Man-Thing. Initially frightened by the creature, the Molecule Man dropped his wand and realized that unless he was holding it, his new body would begin to rapidly age.
The Molecule Man then attempted to leave the swamp but became lost. He then happened upon the Man-Thing again along with the Fantastic Four's Thing, who happened to be in that area searching for the Man-Thing. As a cruel jest, the Molecule Man reverted them back to human form before attempting to escape the swamp again. Reece ended up in the town of Citrusville where the Ben Grimm and Ted Sallis attempted to stop his rampage. The Molecule Man reverted them back to their monstrous forms and tried to pit them against each other. During the battle the Thing tossed a clump of the Man-Thing's muck at the Molecule Man, knocking his wand out of hand. It was too far out of his reach and before Owen could recover the wand, he aged so rapidly his body crumbled to dust. With the wand apparently powerless the Thing gave it to a young boy named Sanford as a souvenir. 
However the Molecule Man was not dead as his mind remained inside the wand, although it was dormant for many months. During this time the boy would play with is friends in the swamps near Citrusville, pretending to by a super-heroes and super-villains. During one afternoon of play, Sanford's friend Cynthia McClellan knocked it into the swamp. Going to retrieve it, Cynthia was chased by a alligator and ran into a pit of quicksand and seemingly drowned. However due to the radioactive properties of that particular area, Owen's mind was awoken from within the wand and used his powers to take control of Cynthia's body, saving her life. Trying to reshape her body into a muscular male form, Owen found that Cynthia's mind resisted the change preventing him from changing genders while in her body. Struggling with her mind, Reece attacked the home where Cynthia and her mother lived. When the heroic Avenger known as Iron Man happened a battle between the two began. However due to Cynthia's idol worship of the Golden Avenger, she forced the Molecule Man to flee. Later, the Molecule Man resurfaced as Iron Man was assisting in the reconstruction of the Omegaville and attacked. During the fight the wand was knocked out of Cynthia's hand freeing her from his control. However a nearby snake happened to attack the wand, allowing the Molecule Man to take possession of its body and transmute it into a humanoid form and resumed his attack. Iron Man tore the wand from the creature's hand and fought against his own possession long enough to hand the wand off to the passing Man-Thing. Since the Man-Think did not possess a mind the Molecule Man could not take control of its body and he was helpless as the Man-Thing wandered off into the swamps. 
Shortly thereafter, the super-villain known as the Klaw materialized in the Nexus of All Realities after his battle with the hero Ka-Zar. He appeared just moments after the Man-Thing discarded the Molecule Man's wand. Recovering, Klaw was immune to possession by Reece due to his inorganic form and agreed to help Reece obtain a permanent body. Learning of Reed Richard's Psi-Amplifier device they went to New York to use it on the Molecule Man's next host body. This body was fond in New York city when the pair happened upon a punch-drunk boxer and forced him to handle the wand allowing the Molecule Man to take control of him.  When they first broke into the Fantastic Four's Baxter Building headquarters the only person present was the visiting Impossible Man, whom they easily knocked out on a sneak attack.  When the Fantastic Four arrived, Klaw and the Molecule Man incapacitated the group and attempted to use the Psi-Amplifier. However the tide of battle began to change when the Impossible Man recovered from their previous attack and fought back. When the Molecule Man attempted to enter the Psi-Amplifier, Reed Richards had enough time to pull the power cable and the feedback caused Reece to retreat back into his wand freeing the boxer from his control. In the aftermath of the battle Reed Richards foolishly picked up the wand, laving himself totally open for the Molecule Man to take over his body.  Although Richards attempted to fight for control of his body, the Molecule Man proved too strong, and in order to save the lives of his teammates, Reed was forced to agree to relinquish control over to his foe. As the Molecule Man terrorized New York City, the Fantastic Four regrouped and attacked their foe anew. When Reed was knocked out in the fight this allowed the Molecule Man take full control and he attempted to unleash the full force of his powers to destroy his enemies. However this plan backfired as his powers could not affect their costumes which was constructed out of Unstable Molecules, causing sufficient feed back to shunt the Molecule Man's consciousness back into the wand and it dropped into a smoke stack where it was seemingly destroyed. 
However it survived and later when the smoke stack was cleared the ashes were dumped in a landfill in upstate New York. Months later a drunken homeless man accidentally came into contact with the wand during an encounter with the Micronaut known as Biotron. Although he was distracted by the fact that he was in possession of the body of an African-American, the Molecule Man sought to capture Biotron and examine him. Their battle took them to a nearby river where Biotron managed to down some power lines. The resulting electrical shock separated the wand from the Molecule Man's most recent host body and was swept down river. 
Sometime after this the wand was found by the Silver Surfer, but when the Molecule Man attempted to possess him, the Surfer's silver skin protected him and he discarded the wand. By this point, Owen decided to try and form a new body through the wand and was surprised when it worked to create him a new body. Restored to human form, the Molecule Man now had the same limitations he had before -- he could not affect organic matter. Intrigued by the Surfer the Molecule Man heard the space-faring heroes origin and was inspired by the tale of Galactus that Owen decided to consume the Earth. Creating a Galactus inspired costume, Owen easily over powered the Surfer and then went to the outskirts of Netoon, New Jersey and constructed a massive fortress to carry out this task. The Surfer then attempted to contact the Fantastic Four with his surf board. However when they were not home, the board was found by the Avengers who then freed the Surfer and went after the Molecule Man. With a barrier blocking their way, Earth's Mightiest Heroes smashed a hole large enough for their new member Tigra to slip through. She confronted the Molecule Man first, and finding that he was an emotionally stunted and insecure man, she promised to get to know him before deciding if she liked him or not. However this did not prevent the Molecule Man from striking back at the other Avengers when they arrived. He destroyed Captain America's shield, Thor's hammer, Iron Man's armor and the Silver Surfer's board before placing them in a crusher device and seemingly slaying them. 
The Avengers secretly survived thanks to the Surfer's Power Cosmic, however they were underpowered without Iron Man's armor and a mystical enchantment that forced Thor to revert to his civilian identity of Donald Blake once away from his hammer for more than a minute. Thinking her fellow Avengers were dead, Tigra attempted to murder the Molecule Man in his sleep but could not bring herself to do it. Despite the fact that they mostly lacked super-powers, the Avengers managed to attack the Molecule Man who fled in fear after being hit by Blake. Ultimately, Captain America incapacitated their foe. As the heroes debated on what to do with him, Tigra managed to convince Owen to get help instead of taking out his anger on the world, and instead use his powers to help people. These words got through the Reece who agreed and used his powers to restore everything to the best of his abilities and surrendered to the authorities promising to go see a therapist to help him with his troubled life. 
Owen soon found himself pulled back into the life of a super-villain when he was one of the many villains gathered by the Beyonder to battle a group of heroes in a conflict that later became known as the Secret Wars. He soon found himself aboard a ship along with Galactus, Latverian monarch Dr. Doom, the time traveler known as Kang the Conqueror, the robot Ultron, the Absorbing Man, Dr. Octopus, the Lizard, the AsgardianEnchantress, and the Wrecker'sWrecking Crew. Among the heroes gathered were members of the Avengers, Fantastic Four, the X-Men, the Hulk, Spider-Man, and the mutant terrorist known as Magneto. They witnessed as the Beyonder wiped out an entire galaxy and created a patchwork world dubbed Battleworld. They were suddenly attacked by Ultron who sought to destroy all living beings on their ship, but Dr. Doom convinced Owen to use his powers to lift Ultron up to Galactus, who drained the robot's energies making it inert. The Beyonder then spoke, telling the gathered super-humans to slay their enemies and they will be given what they desire most. Galactus and Dr. Doom attempted to confront the Beyonder directly and were rebuffed while the others were transported planet side. The villains soon found a headquarters and were reunited with Doom who suggested that they don't follow the Beyonder's decree and instead find a way to steal his power. When they refused, Doom attacked them and fled. Owen joined the other villains in hunting down Doom and found him and the gathered heroes meeting together and attacked. 
Doom escaped in the battle, and Owen and most of the others were forced to flee the battle when the heroes incapacitated and captured the Enchantress, Kang and the Wrecking Crew. When they returned to their base they found Doom waiting there with a body guard -- the reprogrammed Ultron and they were all forced to ally themselves with him and follow his scheme.  Dr. Doom discovered that the city of Denver, Colorado was also part of Battleworld and selected two women Mary "Skeeter" MacPherran and Marsha Rosenberg to endow with super-human powers to bolster their ranks. MacPharran became the power house known as Titania, and Rosenberg the plasma channeling Volcana. Volcana was instantly attracted to Owen and the found themselves forming a fast relationship. Recognizing the Molecule Man's great power, Doom made him his right-hand man and launched a counter attack on the gathered heroes at their headquarters freeing their captured comrades and forcing the heroes to flee.  Owen then used his powers to destroy their base and then levitated an entire mountain and dropped it on the heroes in an attempt to slay them. Similarly when Thor reappeared with the Enchantress, Owen and the others attacked and the thunder god was seemingly slain by Ultron. However the heroes survived these attacks and regrouped a nearby village near where Galactus. 
When Galactus summoned his massive world-ship Taa II to Battleworld to consume the planet, Doom sought to find a means of using the technology aboard the ship to defeat the Beyonder. Meanwhile Owen's relationship if Marsha began to blossom and when the Wrecking Crew attempted to bully the couple, Owen stood up for himself his display of powers frightening the power-houses and convincing them to respect Reece.  When Dr. Doom managed to board Taa II, he ordered his minions to create a series of volcanic eruptions to distract Galactus so Doom could continue to search the ship unnoticed. The Molecule Man joined Dr. Octopus, the Absorbing Man, and Titania on this mission. After they completed plugging up a volcano they were confronted by the X-Men, and during the fight Owen was savagely wounded by the X-Man known as Wolverine and they fled the scene.  When Marsha heard about Owen's injury, she convinced the Enchantress to teleport him to his side. They were once again attacked by the X-Men but this time they forced the mutants to retreat and when they returned to base, Owen was rushed to the medical lab to be healed. 
Molecular Manipulation: The Molecule Man possesses the ability to mentally control, transform, and manipulate the molecules of all matter and energy. Owen Reece gained his extraordinary abilities by mutation through exposure to radiation from an experimental particle generator, which (as later revealed) also opened a "pinhole" into the dimension of the Beyonders, irradiating him with the energy that infuses a Cosmic Cube. Through concentration, he projects a psionic-manipulative energy, the precise nature of which is unknown, that alters the arrangement of molecules according to any visualized pattern. He can animate inanimate materials by causing constant mass movement of molecules: for example, he can make a brick building walk. He can rearrange molecules so radically, he can use his power to reconfigure all forms of matter and them into different substances and forms (such as, for example, turning air into glass), and can change matter into energy and back again. He can create force fields and energy blasts, and also open up worm holes through hyperspace and traverse them, thus travelling faster than light. The maximum area he can affect at a single time is not yet known. In the past, however, he has enclosed the entire island of Manhattan in a plexiglass barrier, lifted a 150 billion ton mountain under his own power alone, converted a two-square mile parcel of land into an ornate palace, and, with assistance from the Silver Surfer, affected the entire planet Earth. Once he effects a change in the arrangement of molecules in a quantity of matter, it remains in its new configuration until he consciously changes it back. Even if rendered unconscious, the transformed substances remain. The Molecule Man can even affect the molecules of matter with mystical properties (such as Thor's hammer), matter fashioned by vast cosmic power (the Silver Surfer's surfboard), and matter composed of the most impervious materials devised by man (Captain America's steel alloy-vibranium shield). The process of molecular manipulation does not cause the Molecule Man any more exertion than performing simple arithmetic. Although the energies that gave Owen Reece his powers came from the same power source as the Cosmic Cubes, Owen Reece generally does not use this capability to the same extent as "true" Cosmic Cubes do, limiting himself to manipulation of "mere" matter and energy. Regardless he has been able to effortlessly recreate an entire galaxy even in his regular state, and on a later occasion unleashed his 'darkest aspect', which possessed sufficient might to fight, and overpower, the Beyonder in a more than 3-dimensional battle, which in turn was claimed by Kubik to be far less than his full potential.
The Molecule Man is a physically below average human being with no athletic abilities or fighting skills.
Originally, the Molecule Man subconsciously imposed mental blocks on himself to prevent his using his powers to their full potential. Hence, he believed his powers were ineffective on organic molecules. Although he overcame this mental block in the past, for unknown reasons he is again unable to control organic molecules. The Molecule Man formerly had a psychological dependency on using a steel rod ("wand") to focus his powers but he subsequently learned how to direct his powers without it. Also, in the past, the Molecule Man has had trouble understanding complex technology, circuitry, and machinery.
The Molecule Man used to employ an ordinary steel rod as a prop to help him focus his powers. He has since learned to direct his powers without the use of a medium. His "son", for as yet unknown reasons, was able to use the rod to affect the molecules of organic matter, a power the Molecule Man himself did not possess for a time.