The size of cells may be as small as a millionth of a meter (micrometer) or as large as few centimeters. Most of the cells are microscopic in size. Cells are not visible to the unaided eye. They can be seen with the help of a microscope. The smallest cell is 0.1 to 0.5 micrometer, which is a bacterial cell. The largest cell is the egg of an ostrich, measuring 170 x 130 mm.
