Children
Cancer is no one's fault -- it just happens. Sometimes people get sick for no reason at all. Cancer is not contagious -- you can't catch it from another person. Cancer happens when a normal cell grows and divides too fast. You can only see cells with a microscope. Here is a picture of a cell:

You can think of cancer this way. If you fall off your bike and scrape your knee, your skin cells kick into gear and start growing to heal your scrape. When the scrape is all gone, the skin cells know they did their job, and they stop growing. But cancer cells don't know when to stop growing. Doctors use three different treatments to help the cells stop growing:

Radiation Radiation beams special energy into cells to stop their growth	Chemotherapy Chemotherapy delivers special medicine into cancer cells to stop them from growing	Surgery Surgery cuts out cancer cells and removes them from the body.