Semiconductor particles in the size rage 1-100 nm have special optoelectronic properties dictated by the quantum mechanics of the potential well. These particles are known as quantum dots. Fabricating structures in this size range has been a great challenge of our time. Self-assembly has become an attractive method to fabricate quantum dots. By 1990, it was known that when Ge was deposited on Si substrate, cube on cube, the Ge film is flat up to a few monolayers, and then forms three-dimensional islands. This mode of growth, from layer-by-layer to three-dimensional islands, is known as the Stranski-Krastanov growth. Many other heteroepitaxial semiconductor films also grow this way. For a while people were studying, both experimentally and theoretically, why this happens and how to grow flat thin film. One man’s trash is another man’s treasure. In 1993, Pierre Petroff, of the University of California at Santa Barbara (UCSB), and his co-workers showed that these 3D islands had the optoelectronic properties of quantum dots. This innovation combined two known facts: heteroepitaxial films are susceptible to Stranski-Krastanov growth, and small semiconductor dots have desirable optoelectronic properties. Since then, the world has been studying how to grow 3D islands.