Diffusion, Presses du CNRS, 1986-1990, Paris. The first picture shows an assortment of phytoplankton, nearly all of which are diatoms which characteristically have a silicate casing called a frustule. The second diagram is a line drawing of phaeocystis poucetti, a coccolithophore. This particular organism is responsible for exceptionally large fluxes of DMS from the ocean into the atmosphere near Europe and Antarctica. The scale bar in the drawing pertains only to the second picture.
Diatoms are typically much larger than coccolithophores and can be seen under low magnification.
The second picture shows electron micrographs of two other phytoplankton species. Notice the scale bars in the photographs. The first example is actually a colony of organisms rather than a single phytoplankter. Clearly, the individuals comprising the colony are very small. These species also produce DMS .