There are millions of species that can't be seen with the naked eye. Scientists have developed many kinds of microscopes to help us to be able to see these tiny denizens—bright field microscopes, dark field microscopes, phase contrast microscopes, confocal microscopes, differential interference contrast (DIC) microscopes, fluorescence microscopes, polarized light microscopes, etc.
The following images are inspired by (but do not accurately depict) some of the more common things you might find by looking at pond water with one of these kinds of microscope.
Ameba
Euglena
Micrasterias
Paramecium
Philodina
Stentor
Vorticella
These fictional micrographs were drawn using Stable Diffusion 2.1.
