Carcinogens are those substances which promotes cancer. These substances induce cancer either by directly affecting the cellular metabolism or DNA damage, thus affecting the normal cellular mechanism. All carcinogens are not mutagens or teratogens. One of the best examples for Carcinogens is a aflatoxinB1 which is produced on Aspergillus flavus, a fungi that grows on the stored grains, nuts and peanuts. It is a naturel microbial carcinogen. Apart from theis microbe, certain viruses like hepatitis B and human papilloma virus are also found to be potent carcinogens. Apart from these molecules, constant exposure to certain type of radiations like Gamma and alpha particles can also induce DNA damage hence damage the cell ultimately resulting in cancer. These chemicals are always advised to be handled with care.