What makes a material child-friendly?

 Is it really the bees or storks that make sexual education fit children? Of course not. The metaphors, jokes and complicated comparisons are rather about the wishes of adults to feel more comfortable to talk about difficult topics. So what should child-friendly materials be like?

This paper mainly focuses on the third question (how). But since you cannot answer this question before you know to whom and what you want to tell, we also cover some important points about the audience and the content.