The term 'microscopic creature' refers to two single-celled organisms, the ameba (5 letters) and the AMOEBA (6 letters). Both are protozoa, which are unicellular organisms that lack a cell wall and have the ability to move independently. The ameba is a type of protozoan found in freshwater environments, while the AMOEBA is a type of protozoan found in saltwater environments. Both organisms feed on bacteria and other small organisms, and reproduce by dividing into two cells. They are both very small, usually measuring less than 1 millimeter in size.