Do you know what is Cancer ? Do you want to know about cancer ? Human body is composed of trillions of cells. Cells are basic structural and functional units of human body. Cells form tissue, tissues form organ and various organs form a human body. Normally cells grow and divide as and when required by body in a systematic process. When cells grow old or become damaged they get destroyed again in a systematic manner. Cancer develops when there is any damage to this systematic process i.e. cells grow and divide without stopping and form growth called tumor. Cancer can arise from any tissue/organ of body. cancer can spread to adjacent tissue or organ , they can spread to lymph nodes or they can spread through blood to other distant parts of body.