Carcinogenesis is the process by which normal cells transform into cancer cells. This transformation typically occurs through a series of genetic mutations that disrupt normal cell growth and division. Factors such as exposure to carcinogens, which are substances that can cause cancer, play a significant role in this process. These can include chemicals, radiation, and certain viruses. The process of carcinogenesis can be divided into three main stages: initiation, promotion, and progression. During initiation, DNA damage occurs, leading to mutations. In the promotion stage, these mutated cells begin to multiply uncontrollably. Finally, in the progression stage, the cancer cells can invade surrounding tissues and spread to other parts of the body, forming tumors.