3Blue1Brown

Grant Sanderson does the thing math teachers rarely attempt: he shows you why a formula is true, not just what it says, walking through the geometry of a proof frame by frame. That approach turned linear algebra and neural networks into genuinely popular subjects — 3Blue1Brown has passed 6 million subscribers who came for calculus and stayed for an animation style now widely imitated across educational YouTube. If you've ever wished a textbook could pause and rewind itself, start here.