The basic unit of cancer lesions is the cancer cell. When a cell in the body ages and dies, it is replaced by a new cell to maintain the body’s function. Each cell knows when to grow and divide, and how to combine with other cells to form tissues and organs. The “drawings” that build the different tissues are genes. Everyone has a proto-oncogene, which is involved in cell division and proliferation and is needed for human growth. In order to “control” it, there are also oncogenes in the body. Normally, the proto-oncogene and the oncogene maintain a balance, but under the action of carcinogenic factors and the accumulation of genetic mutations, the proto-oncogene becomes more powerful while the oncogene becomes weaker. Therefore, cancer-causing factors are the “keys” to initiate the growth of cancer cells, mainly including mental factors, genetic factors, lifestyle, certain chemical substances, etc. Multiple “keys” are used together to start the “cancer program”; the more “keys” there are, the greater the chance of starting it. We have not been able to decipher all the “keys” yet, so we cannot attack cancer yet. Tumor cells are derived from “defective” normal cells and take many years to grow into tumors. The “renegade” cells go off the track and set their own proliferation rate, accumulating to more than one billion before we notice them. The proliferation rate of cancer cells is calculated by multiplication time, one becomes two, two becomes four, and so on. For example, the average multiplication time of stomach, intestine, liver, pancreatic and esophageal cancers is 33 days; breast cancer multiplication time is more than 40 days. As cancer cells keep multiplying, the more advanced the cancer is, the faster it progresses.