[mejutoco]

I vividly remember first day of school after kindergarten in Spain. (3-4 years old?) Sets and Venn diagrams, how interesting and intuitive. Unfortunately it was arithmetic from then on.

[seanhunter]

Fun fact: Venn diagrams were invented by Euler[1]. In fact, John Venn called them "Eulerian Circles" in his papers.

[1] Like so much else in maths.