How many sexes are there? Can you turn a female animal into a male, or vice versa – and why is it not so easy to get rid of the production of male chicks? What have researchers observed after removing the male plants from a plant species with separate sexes – and why do they always stress that you should avoid the so-called “naturalistic fallacy” when talking about gender roles in society and using the word “natural”? These topics are explained using examples from current research.