Sex determination in animals is an interesting topic. While the X and Y chromosomes decide the sex of an unborn baby in humans and most other mammals, external factors like temperature and humidity decide it for the crocodiles and turtles. But what decides the sex of a young zebrafish? Research now shows that a combination of internal and external factors play a role in determining sex in zebrafish. Understanding the process in depth can throw light on some of the intricate workings of nature, say the researchers.