The theory of physics which delves into the physical properties of nature at an atomic and subatomic level is known as quantum mechanics. Quantum mechanics provides the foundations for quantum physics. This includes quantum field theory, quantum chemistry, quantum information science and quantum technology. This field seeks to explain such phenomena which cannot be understood by classical physics. The four most prominent phenomena which quantum mechanics aims to explain are principle of uncertainty, quantization of some physical properties, wave-particle duality and quantum entanglement. The diverse applications of this field include superconducting magnets, quantum optics, electron microscopy, light-emitting diodes, etc. This book is compiled in such a manner, that it will provide an in-depth knowledge about the theory and practice of this field. Such selected concepts that redefine quantum mechanics have been presented herein. Coherent flow of topics, student-friendly language and extensive use of examples make this book an invaluable source of knowledge.