Amino acids can be defined as organic compounds that contain amino and carboxyl functional groups, and a side chain specific to each amino acid. Carbon, hydrogen, oxygen, and nitrogen are the key elements of amino acids. The residues of amino acids comprise the second-largest component of human muscles and other tissues in the form of proteins. Besides their role as residues in proteins, amino acids participate in a number of processes such as neurotransmitter transport and biosynthesis. Amino acids are classified into three categories, namely, essential amino acids, nonessential amino acids and conditional amino acids. They have several applications as active pharmaceutical ingredients, medical nutrition, dietary supplements and cosmetics. The book aims to shed light on some of the unexplored aspects of the amino acids and the recent researches related to the same. Also included in it is a detailed explanation of the various concepts and applications of amino acids. This book will serve as a reference to a broad spectrum of readers.