Each one of us is made up of one hundred million million cells.
That's 100 000 000 000 000!
There are 200 different types of cell - they all do different jobs, have different shapes and behave differently. Because cancer is a disease of cells, this means there are also over 200 different types of cancer!
The pictures below show different types of cells. The cells on the left are red blood cells. The cells in the middle are hair cells from inside the ear. The cells on the right are fat cells.
You can read more about cells and how they work in the sections below.
Chromosomes, genes and proteins
All images were kindly provided by the EM Unit at the London Research Institute and the Science Photo Library.