Green algae. 1000x magnification. Brightfield microscopy.

I don’t know the exact ID of the different organisms in here, but most of them appear to be Chlamydomonas sp. Although most other algal lineages are classified as protists, chlorophytes (part of the green algae) are often considered members of the plant kingdom. In fact, the evolutionary ancestor of land plants was likely a filamentous green alga. Some reasons the green algae are classified as plants are because they possess cell walls made of cellulose, use chlorophyll a and b in photosynthesis, and have some plantlike reproductive mechanisms. Although you can only see it under the microscope unless you have a scummy bloom, green algae are a type of microalgae that has many practical uses. You can find it as an ingredient in lots of different green juices, as a dye, as feed for animals in the aquaculture industry, various pigments have been used as dietary supplements, secondary metabolites have been used in biomedicine and drug development, and some strains have potential in the biofuel industry. And of course, all algae are primary producers that contribute significantly to carbon cycling and global oxygen production. Without these tiny organisms, we wouldn’t be able to breathe!