Actions of living beings at any stage of life are of general interest; molecular machines can be a replica of such activities. Stimuli guided movements and shape changes of molecules are one of the rapidly developing areas on which fundamental principles of molecular machine banks. Thus, the understanding of intriguing concepts of molecular machines is essential. Miniaturization, efficiency, stability and robustness in performing activities are some of the important points associated with molecular machines. Using molecular machines for practical purposes will further strengthen fundamentals of science and technology and also guide future market economy. Recent advent of techniques to handle materials at microscopic level has benefited the topic of molecular machines and is ready to be taken to a higher level as compared to other competing topics of science and technology. Molecular machines is a contemporary hot topic with future scope. The Nobel Prize in the year 2016 was shared by three scientists Prof. Ben Feringa, Prof. J Fraser Stoddart and Prof. Jean-Pierre Sauvage for their contribution to the topic. This book on molecular machines is aimed to cater to the need of graduate students and researchers by providing the fundamental aspects on molecular machines.