In the first part of my talk I will introduce the idea of atomic clusters as superatoms and magnetic superatoms, and will present two classes of binary metal clusters that behave as magnetic superatoms. I will then explore, using electronic structure calculations, the right substrate for assembly of a particular magnetic superatom FeCa8. In the later part of my talk I will show some results on adsorption and diffusion of silver clusters on clean and stepped graphite substrates. These results give atomistic insights into some of the experimental observations on these systems.