It is the presence of local variations in atomic and electronic structure that often gives rise to intriguing properties of materials. Control of material properties then rests on detection of the local variations in the materials, determination of the origin of those variations and then understanding how such variations can be controlled to achieve a desired functionality. Recent examples using STEM with an atomic sized probe (∼2.2 Å) include studies of the bonding at grain boundaries in nickel rich Ni3Al doped with boron. EELS measurements revealed changes in the d-hole density-of-states that were used to estimate changes in the electronic contribution to the grain boundary energy. These changes in grain boundary strength correlated with a change in fracture from an intra- to an inter-granular mode. In another example, the observation of metal induced gap states at Cu/MgO interfaces provided evidence that the dipole moment across that interface was relatively low.