Fractional differential equations or fractional order differential equations are generalized and non-integer order differential equations, which can be obtained in time and space with a power law memory kernel of the non-local relationships. They are also known as extraordinary differential equations. They are used to describe the functioning of various complex and non-local systems with memory. Fractional differential equations are applied extensively in various fields including medicine, mechanics, control theory, signal and image processing, environmental science, mathematics, physics, chemistry, and biology. Some of its prominent applications include time-space fractional diffusion equation models, acoustic wave equations for complex media and electrochemical analysis. This book covers the latest researches on the theory and applications of fractional differential equations. It strives to provide a fair idea about these equations and to help develop a better understanding of the latest advances in their study. The book is an invaluable asset for researchers working in the areas of pure mathematics, applied mathematics, statistics, and engineering.