Does a larger organism have larger cells? You might expect a big animal to have bigger building blocks than a tiny plant. But cells do not always scale with body size. You measure cells from different organisms under a microscope. Human cheek cells average about 70 microns. Human vein cells average about 47 microns. Spinal cord cells come in near 57 microns. Then you measure cells from two plants. Elodea (a common water plant) has cells averaging 242 microns. Wild algae cells average 174 microns. The smallest organism in the group has the largest cells. Body size does not predict cell size.