Art 21 was founded in 1997, during my second year of grad school. Back then, it was only on PBS. Eventually, you could get a DVD of the films, as well as a book...which I did! Now it's a massive online archiving nearly 30 years of documentary films about the worlds most important artists. You can see inside their students, and hear them discuss their work, process, and motivations. I've used these films in my classes for about as long as they have been in existence. Super duper highly recommend, even for art world veterans.