Cells are the structural and functional units of all living organisms. Cells are also part of the human body. Cell can kill human being. When cell begin to grow out of control its produce cancer. Cancer is name of one of a deadly disease that can kill human being. People can inherit cancer, DNA [d (eoxyribo) n (ucleic) a (cid).] A nucleic acid that carries the genetic information in the cell and is capable of self-replication and synthesis of RNA. DNA consists of two long chains of nucleotides twisted into a double helix and joined by hydrogen bonds between the complementary bases adenine and thymine or cytosine and guanine. The sequence of nucleotides determines individual hereditary characteristics. When DNA damage cancer cell develop. Most of the time when DNA becomes damaged, either the cell dies or is able to repair the DNA.DNA gets damage because of our environmental problems, like chemical waste that not properly throw, to much smoking, and different kind of viruses that can get in our environment and one more things too much exposed in sunlight. Cancer can prevent by changing lifestyle .If you are a smoking person avoid it, because there is lot of possibilities to have lung cancer, practice sun safety if you love sun bating or those people too much exposed in sunlight can cause skin cancer, Eat good food like Fruits and vegetables that are rich in antioxidants that can help to repair damage cell. Avoid drinking too much alcohol or any kind of liquor. Exercise is one of the best things to do to prevent cancer. Practice safe sex all the time. Remember it is better to prevent than to cure.