Using spontaneous self-organization effects is an efficient way to produce nano-structures, as for instance quantum wires and quantum dots. This article is focused on the strain-induced self-organization, or ''self-assembling'' effect, producing quantum dots. Particularly the following aspects will be addressed: (i) the phenomenology of the 2D-3D morphology transition, (ii) the effects of materials choices and growth conditions on density, size and homogeneity of dots, and (iii) manipulations to get laterally aligned and vertically stacked dot structures.