Cancer causes uncontrolled growth and spread of malignant cells, so think of the disease as first occurring at the individual cellular level.
What's a Cell?
Cells are the building blocks of human beings. They give our body structure, convert food into energy and handle all sorts oftasks necessary to sustain life.
How Many Are There?100 trillion per person. If a cell was the size of a dime you would need 100 trillion dimes to fill up the Empire State Building.
Where's The Nucleus?
At the core of every cell. The most important item insidethe nucleus -- for purposes of explaining cancer -- are the genes.
Why Are Genes So Important?
Because many scientists think that cancer is 
caused by defects in our genetic material. The information that makes up each gene is encoded on chromosomes that are part of molecular strands known as "DNA."