CELLULAR DIVERSITY: Cells of different tissues and organisms exhibit an array of dramatically different shapes and sizes. Here, clockwise from top left: retinal rods and cones, stacked red blood cells, Purkinje cells in the cerebellum, sensory hair cells in ear, the unicellular protist Stentor coeruleus, and the corneal endothelium.
When we first learn about cells in grade school, we’re told to imagine them as “blobs.” And indeed, some cells really are blob-shaped, perhaps most famously the amoebas that ooze across the bottom of a pond engulfing smaller organisms. Most of the tissue culture cells that serve as workhorses for cell biology research, such as HeLa cells, are also pretty bloblike. But if we stop looking at cells grown in a dish and start examining those found inside the human body, we are immediately struck by the wide range of beautiful and intricate shapes.
Cell interiors are also full of three-dimensional geometric complexity. Cells aren’t just watery bags of enzymes, but rather are compartmentalized into a large number of organelles, each of which carries out ...
