With the entire human genome sequenced, we have the increasing capability to map the connections between genes and the traits or diseases they control, and for increasing the capacity of testing and treatment. This section examines how scientists use a revolutionary tool, the microarray, to determine how genes are functioning in a particular genome, and explores the complex choices introduced by this new technology—such as whether to test for genetic predisposition to a certain disease. For decades, prenatal testing has offered expectant mothers and fathers a sneak preview of their babies' health. Now more and more inherited disorders can be detected by genetic testing—and all of us can learn what lies within our genes, at any point in our lives.