In recent years, nanotechnology has become one of the most important and exciting forefront fields in Physics. It shows great promise for providing us in the near future with many breakthroughs that will change the direction of technological advances in a wide range of applications. Nanotechnology is the study of manipulating on an atomic and molecular scale. Generally nanotechnology deals with developing materials, devices or other structures possessing at least one dimension sized from 1 to 100 nm. In this book pure CdS and transition metal ions doped CdS semiconducting nanomaterials were synthesized by microwave-assisted solvothermal method. To prepare the pure CdS nanoparticles, we choose thioacetamide as the sulphide source. It is much easier for thioacetamide to release sulphide ions. This will be beneficial to lower the reaction temperature and shorten the reaction period. And also we choose the nontoxic, ethylene glycol as the solvent. This is more favourable to the environment. The microwave treated precursor materials, after washing with de-ionised water and alcohol and after annealing leads to fine nanocrystalline powder.