Understanding the motion of more than 2 planets evolving under the gravitational law is a long-standing problem in mechanics and mathematics. It lead to the discovery of deterministic chaos at the end of the 19th century. However, existence of chaos does not mean that nothing can be said about such systems. Restricting to situations where the system has 3 degrees of freedom, one can use tools coming from 3-dimensional topology, like knots and surfaces, in order to describe the dynamics. We will discuss some examples, in particular using the notions of open book and broken books.