A molecular beam is created when a gas expands from a higher pressure region to a lower pressure region through a small opening. It is used to directly measure uptake on a prepared surface as well as to provide information on the scattering of molecules from surfaces. These techniques have been widely employed to evaluate reactive and non-reactive uptake of radical and non-radical species on ice and water surfaces. The creation of the supersonic molecular beam, which is produced by a free jet expansion source, has significantly increased the versatility of the molecular beam technique. This book is a valuable compilation of topics, ranging from the basic to the most complex advancements in the science and engineering of molecular beams. It consists of contributions made by international experts. A number of latest researches have been included to keep the readers up-to-date with the global concepts in this area of study.