The human body is more sophisticated than even the best computer. But while scientists know more about the human body than perhaps anything else, there are still mysteries that baffle us. When it comes to the human body, the more we know, the more we realise we don't know! The human body is a collection of 100 trillion tiny cells. These are the body's building blocks. Each cell has the same basic structure: an outer skin, a nucleus, and a jelly-like fluid containing floating organelles. There are many different types of cells: fat cells, blood cells, brain cells and more!