The Ant-Man (Marvel) has this power.
The Wasp (Marvel) was a partner of Antman in the Official Handbook of the Marvel Universe V1 #12.
The Atom (DC) has this power.
Shrinking Violet (DC) can even shrink to subatomic size (DC Who’s Who #21).
Shrinking Ray’s (Image) name is probably an homage to Brainiac’s Shrinking Ray (DC) in the Official Handbook of the Invincible Universe #2.
What if there are worlds within worlds literally? Many have noticed similarities between the solar system and an atom. Is our solar system an atom in a larger world? Do atoms have life forms similar to us?
Are we inside an atom inside a giant brain?
The Marvel universe has a Microverse (a subatomic universe with life forms) with a long and intricate history. The Marvel Microverse is first introduced but not named in Fantastic Four V1 #16 (Marvel).
The Fantastic Four then has several adventures in Sub-Atomica which is later established as a part of the larger Marvel Microverse (Fantastic Four V1 #76).
The Micronauts (Marvel) are recurring Marvel characters that inhabit the microverse (Micronauts V1 #1).
Below is a map of the Microverse from Micronauts V1 #24 (1980) but the map does not include Sub-Atomica.
The DC has a much less developed microverse than in the Marvel universe.
The Atom (DC) could have had many adventures in a microverse but only had one in The Atom V1 #32 (DC).
Superman (DC) is introduced to a one-shot microverse character called Roga (DC) who is from the subatomic Nortuiian realm (Action Comics V1 #479).
The Hornet (Savage Dragon) resembles the Wasp (Marvel).
Cassandra Lang (Marvel) aka Stinger and the daughter on one version of Antman (Marvel) and has the same powers more or less as dad!
Lonely Mountain – 100% Biodegradable #10 (Biomekazok)
Nanomech (Ben 10)
Tiny Harold (Marvel) proves that small is beautiful in Silver Surfer V7 #8.
Inner Space can shrink in Space Girls – 2000 AD #1062
Make sure to read: Size Lessons in Comic Books
Next Skeleton Mimicry