The Danes are quite frank to their children regarding sex from early days only and perhaps everyone should follow them too. According to them everyone should learn to use proper words when describing bodies promotes a positive image regarding bodies and also increases self-confidence and improves communication between parents and children. Redditor Sara cannot imagine any other better way to learn about sex and tells that during childhood her parents described her about birth process in the most proper and scientific way which will describe it as a good learning. This for her is the best way. So have a look at these pictures in this link.
More info: Amazon | AuroraSinistra (h/t: upvoted, boredpanda)