Abstract
A review is given of the nucleation and growth processes occurring in thin film formation. Emphasis is given to quantitative nucleation theories and to the role of electron microscopy and surface techniques in providing data to test such theories. The relations between the thermodynamics of adsorption and the kinetics of crystal growth is stressed. Experimental examples are taken from the island growth, layer plus island (or Stranski-Krastanov) and layer growth modes. The shapes of growing crystallites are briefly discussed.