We will collect a very small amount of fluid from each testicle. Participation will last up to 12 weeks. The study involves a minimum of 4 visits, the screening visit and procedure Day, fine needle aspiration of the testes (about 1-1.5 hours each) and two follow-up visits (about 30-45 minutes). Over the course of the study, you will have a little less than a 1/3-cup of blood drawn (roughly 2-3 tablespoons at each visit).