Building blocks are at the foundation of all construction toys (no pun intended).

Although the concept of using wooden blocks as toys for children to build and play with has probably been around for centuries, "the earliest mention of building bricks for children appears in Maria and R.L. Edgeworth's Practical Education (1798). Called "rational toys," blocks were intended to teach children about gravity and physics, as well as spatial relationships that allow them to see how many different parts become a whole" (1)

(1) http://en.wikipedia.org/wiki/Toy_block