This book presents a detailed account on the domain of measurements in quantum chemistry. Quantum mechanics is considered as one of the most exceptional development in 20th century physics. Every successful theory is exclusively concerned about "results of measurement". In measurement, quantum mechanics perspective is a stark contrast from classical physics because in the microscopic world of quantum mechanics, a direct measurement, like in classical forms, is impossible. Hence, measurement has posed significant challenges over the period of development of quantum mechanics. This book has been compiled by contributions from international experts and aims to clarify various interpretations about measurement in quantum mechanics.