Ever since the Human Genome Project was pronounced complete scientists have believed that most of our DNA was useless, perhaps a vestige of evolution. Now, over 400 researchers working in over 30 labs have jointly announced what the rest of that DNA — over 90% of our total genetic material — actually does. It acts as switches for the business part of our DNA: the genes which code for our appearance, intelligence, and which diseases we will get. This affords scientists a window into how genes work and how we can control them. What does this mean for cancer research and treatment? Differences between normal and cancerous genes have been exploited in recent years to yield scores of new drugs to control cancer. If we come to understand how switches are normal or abnormal we will be able to develop a whole new class of anti-cancer agents, at least some of which could be expected to prevent cancer in people with abnormal switches. So far there are no clinical or therapeutic implications of these observations, but a raft of meetings and publications scheduled for the next year will open up this field to thousands of researchers who will be targeting these switches for manipulation. This is the most exciting development in human biology since the Human Genome Sequence was announced. Stay tuned.