I will introduce Rydberg atoms and their mutual interaction which can be of van der Waals or dipolar character. This interaction leads a blockade mechanism which is observed in a BEC. We will see that this strong interaction will allow us to emulate the ground state properties of spin Hamitonians as they are discussed in condensed matter physics. Universal scaling behavior in the quantum critical region of the underlying phase diagram is observed. The laser excitation to the Rydberg state can be coherent despite strong interactions. To prove this experimentally rotary echo sequences are applied.