Ray Palmer, a physics professor who created a belt to shrink himself down to sub-atomic size while maintaining his mass, was the Silver-Age Atom. According to DcWikia.com, Palmer's first appearance was in Showcase #34 (1961).
Below, BootLego Atom with my BootLego Flash- what a pair of DC Comic's finest ...!
See my January 2013 post featuring the DC Action League Atom and Flash!
More Later- Make It FUN!