I recently watched Lego's "Brickumentary" (http://www.imdb.com/title/tt3214286/ http://www.imdb.com/title/tt3214286/)... according to the movie, Lego's major in

I recently watched Lego's "Brickumentary" (http://www.imdb.com/title/tt3214286/ http://www.imdb.com/title/tt3214286/)... according to the movie, Lego's major invention was putting cylinders inside the bricks, which allow them to be stacked in all kinds of ways. I think that qualifies for a patent.