Here are some of my favs:
3Blue1Brown: Mostly maths, some physics. His USP is lovely visualisation, and he makes an effort to make very cool cutting-edge maths ideas understandable to anyone who's done some high school maths. (Because the important thing is thinking creatively, not just knowing lots of maths facts.) Also, he has a really nice voice.
The important thing to know is that they assume little to no background knowledge, just curiosity. But their videos are equally engaging to my researcher friends as well as people who work in totally unrelated areas.