In 1972, Takara released a series of 8" and 12" action figures named Henshin Cyborg ("Transforming Cyborg"). The Henshin Cyborg line was a spin-off of the earlier Combat Joe line. The Combat Joe line was created from the mould of the 8" and 12" G.I. Joe figures that Takara licensed from Hasbro. The body of the Henshin Cyborg was molded in clear plastic to expose the gleaming inner cybernetic implants and the "atomic engine".
Since the cost of producing the vehicles and playsets for the 12" dolls was prohibitive, as well as taking up space in living rooms, Takara decided to produce a miniature version of the Henshin Cyborg line which was called Microman.
The first series, Microman Zone, included four figures and several vehicles in kit form that needed to be assembled. Microman Zone proved to be popular and by its second year, the Microman line was spun-off from the "Henshin Cyborg" line.
Unlike other toylines at the time, Microman figures were marketed as being the "actual" size of the real thing. Microman figures were cyborg beings from the planet Micro Earth that disguised themselves as toys. All of the Microman toys used 5 mm connectors and ports, which allowed parts from one toy to be attached to another toy to form new toys.
Recently, Takara has expanded the Microman brand to include various licensed brands, including Batman (comic-based and Batman Begins), Superman (comic-based and Superman Returns), Evangelion, Street Fighter, Godzilla, Alien vs Predator and Ultimate Muscle. (A Spider-Man toy had been announced at one point, though no pictures ever surfaced; its product number eventually went to one of the Predator figures.)
What's it worth? Take a look at this Microman price guide: sold listings for a value indication.