Nanomaterials have been studied intensively in the last two decades with realization that the electronic, optical, magnetic and chemical properties of nanocrystals depend on their size has motivated rigorous research in this area. At the nanometer scale, the atomic and molecular interactions may strongly influence macroscopic properties of materials, resulting in changes in mechanical, electrical, and optical properties. In modern electronic devices, quantum dots based nanostructured devices plays a vital role because of their promising applications in electronic and optoelectronic devices such as organic field effect transistors, light emitting diodes, photovoltaics and non-volatile memory devices. In this book preparation and characterization of CdS and CdSe nanocrystals are discussed.