In the last ten years observational work has clearly answered the question as to WHETHER planets exist around other stars, now we must move onto the question of WHY they exist, addressing the physics of planet formation itself. Whilst there has been a great deal of theoretical activity in the area, the observational constraints are poor, in part because it there are at present no good techniques for following the planet formation itself in detail. The best way to constrain the theories, therefore, is to study the environments in which the planets form, following the evolution of the planetary discs, stellar rotation and related properties. Studying a single young cluster will yield a large sample of stars with homogenous properties. Studying many clusters allows us to study variation of planet formation as a function of those properties. Such meta-studies have now been made possible by the new generation of sky surveys, which yield homogeneous data for large numbers of clusters. The PhD will involve us- ing these, in combination with new techniques developed in Exeter for determining ages of the clusters, new data from large telescopes and interaction with Exeter theorists to learn from observations what controls planet formation.