When investigations on semiconductor nanocrystal quantum dots started more than a quarter of a century ago, no one ever believed that nanoparticle research would develop into one of the major fields in modern science. The basis was laid by studies of photocatalysis and artificial water splitting driven by the former oil crisis. These euphorically started activities ebbed away more and more when on one side oil brimmed over again and the scientists on the other did not succeed in the concomitant formation of hydrogen and oxygen. At the same time size quantisation was discovered in nanocrystals...