More people should read Oliver Sacks' book Uncle Tungsten. As a kid he was allowed to buy real chemicals for his chemistry set and was told things like "can you make slightly less hydrogen peroxide next time". Minors buying pitchblende (Uranium ore) at the local drugstore for experiments? Sure, might encourage them to be scientists.

I think the first time my son said the 'f' word, he got the tone and the body language exactly right for the context in which he used it (a frustrated/resigned "fuck's sake", with roll-eyes and throw-head-back, look up to the sky). He might have been five years old at the time. And back then, I really didn't say it around them very much (out of an attempt to be somewhat responsible).

They're absorbing everything. They're scraping the entirety of your personality to build their own.