AbstractThis article provides an introduction to the growth by molecular beam epitaxy (MBE) of semiconductor structures which have dimensions of the same order as interatomic distances in solids. The basic process technology is first described, followed by a brief account of surface reaction mechanisms involved in the growth of GaAs from an atomic beam of Ga and molecular beams of As4and As2.From the study of growth dynamics using electron diffraction techniques it is shown how reduced dimensionality structures can be grown and some indication is given of the effects of quantum confinement on material properties. Finally, some recent modifications of MBE based on flux interruption are described.