Dr. Stephen J. O'Brien directs a research laboratory at the National Institutes of Health and is a coDirector of The NOAHS Center for Basic Research on Conservation at the Smithsonian Institution. At what age did you choose your career? I chose to be a geneticist at age twenty. Was there a specific event or person associated with that decision? There was a college teacher who was absolutely critical in introducing me to the wonder of the new genetics. What has been the greatest experience of your career? Learning about animal secrets by studying genes in cheetahs, lions, tigers, and other wild cat species. The more we understand about animals, the more we know about human biology and ourselves. Animals teach us many secrets on how to solve medical puzzlements. What specialized skills do you need for the job? A burning thirst for knowledge; advanced training in molecular biology and genetics; a strong ability to communicate and interact with others; good writing and speaking skills. What is the most frustrating part of your job? That all of the easy research questions seem to be already solved, so those remaining are big challenges; in some cases we simply cannot solve them. Any advice for young people who are considering a career in zoology? Go for it, because with today's technologies and opportunities, I cannot think of a more challenging and exciting way to spend your time and even get paid for it! If you could be any cat, which would you be? Pallas's cat, a wise and handsome old character.