The Japanese toy company Takara made a toy series in 1974 called Microman that was a miniature spin off of their Henshin-Cyborg1 figure. Interestingly, this figure was a modified doll produced in recycled molds originally used to produce Hasbro toy company's G.I.Joe doll. The Microman toys were made in a smaller 3.75 inch figure that had a similar level of articulation to the 12 inch GIJoe. These smaller toys had the advantage of being cheaper to produce as well as allowing a play pattern that included vehicles and accessories that the larger size prevented for cost reasons.
The story of the Microman toys in the US is a very tangled web of toy lines and companies. When the toys were imported into the US they were divided into different lines by different US companies. In the US these toy lines became very popular in their own right. Two popular US toy lines to come from the Microman toy molds. The first is the 3.75 inch action figures and some accessories imported by the Mego Corporation that where known in the United States as Micronauts. The other US toy line adapted from Microman started when some smaller transforming vehicles were imported to the US by Hasbro and combined with another, similar Japanese toy line known as Diaclone to become know as Transformers. (Wikipedia)