Surface science studies allow processes impor tant for heterogeneous catalysis to be investigated in greatest detail. Starting from the simplest model of a catalytic surface, a metal single-crystal surface under ultra-high vacuum conditions, enormous progress has been made in the last decades towards extending the surface science of catalysis to technically more relevant dimensions. In this perspective, we highlight recent work, including our own, dealing with the influence of water on metal-support interactions in surface science studies of oxide-supported metal nanoparticle model catalysts. In particular, the effect of hydroxyl groups on nucleation and sintering of metal nanoparticles, and surface science investigations into catalyst preparation using wet-chemical procedures are addressed.