Dr. Takahashi describes the powerful strategies that he and others have harnessed for understanding biological clocks in mammals. To tease out the secrets of how the clocks in higher organisms function, scientists had to overcome uncommonly high hurdles posed by the complexity of mice, hamsters, and humans. Many of these studies used the increasingly important research tools of genomics and computer-based informatics. One payoff already is a better understanding of human sleep disorders that are linked to specific genes.