The world where we live has one important general feature: it is made of three dimensional objects, i.e. of objects extending over macroscopic lengths in three spatial dimensions.

This has important consequences on the physical properties of the objects as well as on their functioning in devices. Suppose now to cut the objects so that along one or more spatial dimensions the length amounts to few 1000 atoms (mesoscopic scales) or few atoms (nanoscale): how does the physics look like at these scales?
This is the essential question we are trying to answer.