One of the major and basic/fundamental problems in arithemtic geometry is to understand the Galois theory of the field of rational numbers. In his "Esquisse d'un Programme" Grothendieck proposed -among other things- a new way to look at this type of questions: The absolute Galois group of the rational numbers should finally have a topological / combinatorial description. In my talk I will explain what this precisely means and give a short survey of the state of the art.