The spread of cells from one organ to another organ is the main cause of death for cancer patients. When cancer cells continue to grow and form a tumor some of them run out of oxygen. Cancer cells learn to deal with these low levels of oxygen by switching on genes that help them survive even under stress. As a result, rather than dying these oxygen-deprived cells become even more powerful and can continue to survive even when treated with cancer drugs. To investigate how these cells function we must find these powerful cells within a tumor. To do this we designed a trick to make the cells change color when they do not have enough oxygen. We can use this color to find and collect the cells from within a tumor. Once we collect the cells, we will try to determine what makes them so powerful and use this information to try to design methods to kill these deadly cells.