This interactive animation can be used to compare the relative sizes of cells and organisms ranging from 2 millimeters to 20 nanometers. It initiates with a human hand holding a pin. Zoom in to see a human hair, dust mites, pollen grains, and red blood cells on the pinhead. Continue zooming and to get a sense of how very tiny bacteria and viruses are compared with a grain of pollen. This resource is part of a larger collection of interactive animations created for the life sciences by the Cells alive! library collection.