The largest human cells are about the diameter of a human hair, but most human cells are smaller and might be one tenth the diameter of a human hair. Run your fingers through your hair now and look at a strand of hair. Look down at your little toe - it might be 2 or 3 billion cells or so, depending on how big you are. Imagine a whole house filled full of baby peas. If the house is your little toe, the peas are the cells.
Bacteria are about the simplest cells that exist today.
A bacteria is a single, self-contained, living cell. When you get an infection, the bacteria are swimming around your big cells like little rowboats next to a large ship. Bacteria are a lot simpler than human cells. A bacterium consists of a outer wrapper called the cell membrane , and inside the membrane is a watery fluid called the cytoplasm . A E. Coli bacterium has a distinctive, capsule shape.