I always enjoyed geometry a lot, I still remember my first courses on Euclid’s geometry at school. Struggling with congruent triangles, circles and polygons, trying to understand the Pythagorean theorem and to compute the area and the volume of various geometric objects. There is though something that I learned much later by coincidence, and I very much would have liked to have seen it earlier. It is a result from geometry, called Euler’s polyhedron formula, about geometric objects on the plane and in space. It is a mathematical equation that relates the number of faces, denoted by F, the number of edges, denoted by E, and the number of points, denoted by P, of a polygon or a polyhedron. Euler’s polyhedron formula in some sense shows that most of the geometric objects around us share a common characteristic. Let us see how it works.