While strolling around NY (New York – Manhatten) I noticed a really pretty donut looking at me. I got really impressed with it’s design and colour set. This donut remembered me my, Advanced Math course back in the days I was studying, where we represented mathematically a torus. I opened my phone and viewed it’s equation without any cost. It was free and imediatly available in wikipedia. For me, one of the most marking human accomplishments in my life time. Everyone knows it! And in some direct or indirect way we use it (our children use it).