Superlattices are solid, periodic arrays composed of nanocrystals with very narrow size distribution of weakly interacting nanocrystals. The narrower the particle size distribution, the easier it is to obtain long range super lattice ordering. There is delicate interplay between interparticle attractions where it is strong enough to drive superlattice crystallization, yet weak enough to allow annealing. The macroscopic properties of the nanocrystal superlattices are determined not only by the properties of each individual particle, but by the interaction/coupling between the nanocrystals interconnected and isolated by a monolayer of thin organic molecules. Also the thickness of the organic layer influences the properties.