Atom vs Ant-Man
Ray Palmers’s version of DC’s The Atom debuted in 1961. The physicist via a mass of white dwarf star matter is able to shrink his body down all the way to subatomic levels while maintaining his normal strength and also grow his body and also manipulating his density.
The following year, 1962, Marvel introduced Dr. Hank Pym aka Ant-Man who is a biophysicist discovers a chemical substance that allows him to alter his size. The aptly named Pym-Particle allows Ant-Man to shrink down to subatomic levels and increase his normal size. Ant-Man has superhuman strength and agility and possesses a helmet that allows him to communicate with ants. Ant-Man is a founding member of the Avengers.