Contact structure on a 3-manifold is a nowhere integrable plane field. In the 70’s Thurston and Winkelnkemper showed how an open book decomposition of a 3-manifold gives rise to a compatible contact structure. In 2000 Giroux showed that every contact structure on a 3-manifold is compatible with an open book decomposition.

Ozsvath and Szabo used this fact to define an invariant for the contact structure in their Heegaard Floer Homology. We will describe a simple way to visualize this invariant and talk about applications and generalizations.