Cancer can be a scary word, but it doesn't have to be.
It's a disease that's been around for millions of years. Cancer has even been found in dinosaur bones!
The ancient Egyptians had it and the Greeks even came up with its name - it means "crab".
It is a common disease and it is likely sometime in your life you will know someone who is affected by it.
There are over 200 different kinds.
Cancer happens when a small bit of how a cell works or behaves goes wrong.
The human body is made up of hundreds of different sorts of cells which all have different jobs to do to make the body work.
When cells go wrong, they grow the wrong way and they can start destroying healthy body tissue.