In this video, we're going to begin our introduction to cell cycle regulation. So, the cell cycle, which includes cell division, is actually really highly controlled and regulated. A cell is not supposed to divide whenever it wants; a cell is only supposed to divide whenever it receives the appropriate signals for it to divide. Cell division is actually activated by a variety of cellular signals in the form of proteins called growth factors. Growth factors can be defined as a biological substance that promotes cell division. Once again, a cell is not supposed to divide whenever it wants. A cell is only supposed to divide whenever it receives the appropriate signals that promote cell division. In addition to the growth factors that can trigger cell division, there are also multiple cell cycle checkpoints that are very important in the regulation of the cell cycle. As we move forward in our course, we are going to talk more about these cell cycle checkpoints. Ultimately, these cell cycle checkpoints act like little stop signs for a cell. The cell will actually stop at these checkpoints, and the checkpoints are going to prevent the cell from entering the next phase prematurely. The checkpoints are a way for the cell to stop and check to make sure everything is okay and ensure that there are no errors before it proceeds into the next phase. If an error is detected at any checkpoint, then a protein called p53 can either trigger the repair of the error or, if the error cannot be repaired, trigger another process called apoptosis. Apoptosis is programmed cell death, which can actually be a good thing, even though it may seem like a bad thing when cells die. Apoptosis, or cell death, would be triggered if too many errors accumulate, and by the cell undergoing apoptosis, it's preventing the accumulation of errors. Apoptosis can be a good thing under the right scenario. Really, it's a cell that ignores these cell cycle checkpoints that can lead to problems, specifically, the development of cancer. Later in our course, we will also talk more about cancer. As we move forward and talk more about these cell cycle checkpoints, it's important for you to keep in mind that these checkpoints are very important for regulating the cell cycle to ensure that cancer does not develop. This concludes our introduction to cell cycle regulation, and as we move forward in our course, we'll talk about these cell cycle checkpoints. So, I'll see you in our next video.