In all these cases, cells' genetic material is permanently damaged. Normal human skin and blood cells develop and divide as they are needed. They also die off. The system is a tightly regulated by cellular genetic material. Yet if just one cell's regulatory mechanism goes haywire, cancer can develop. Cells begin to divide in an uncontrolled way and tumors begin to grow. In the end, cancer cells can even become separated from the tissue where they originated and move to other parts of the body, where new tumors, known as metastasis, can develop.