Coccolithophoridae are a type of single-celled phytoplankton (marine algae) that live inside complex shells made of calcium carbonate. The White Cliffs of Dover are made of countless numbers of coccoliths, the individual plates that form the shell. This specimen was filtered from tropical seawater and colorized in two different color schemes to illustrate the fact that all electron micrographs are initially monochromatic. SEM x 18,000.