The world we live in is made of atoms and most atoms have 2 or more stable isotopes. This book discusses the isotopic diversity of chemical elements under the unifying idea of "isotopicity." That allows to describe in a singular way a broad range of effects of isotopic randomness in the physics and chemistry of solid and liquid systems, material science, nano-technology and engineering ("isotopic engineering"), biology, informatics, quantum computing, etc. The book can be equally read by professionals (scientists, academics, students, engineers) as well as by a broad segment of the lay public