What is a cell?

Cells can vary greatly in size, although they are usually so small that you need to use a microscope to see them.

Examine the image below which compares different cell sizes and shows what type of microscope you might need to use to view the different cell types.

Human cells

Red blood cells are some of the smallest cells in the human body. The cells in this image have a diameter of 0.008mm. This means that if you were to line up 125 of these cells next to each other, the line would only measure 1mm long!

Plant cells

Plant cells are usually larger in size than animal cells. The cells in this image are from the skin of an onion. Although they are larger than the red blood cells in the image on the left, you would probably still need to use a microscope to see them in detail.