Textbook in PDF format Nanomaterials have been part of our world for centuries, although it is only in the last 30 years that we have come to understand that the colour of nanomaterials is tied directly to their size, opening up a new realm of discovery. By controlling the size of nanocrystals, chemists have joined forces with physicists and theorists to explore the extraordinary and unexpected properties of nanomaterials. In particular, these properties depend not only on the size of the nanomaterials but also on their shape and the way in which they are assembled into crystalline networks. This book traces the remarkable journey that led to this discovery. This journey into the nanoworld invites both budding scientists and anyone fascinated by advancements in science to explore a universe where no prior knowledge of chemistry or physics is required, only curiosity and a willingness to embrace unexpected discoveries across various scientific domains. This book emphasizes how foundational concepts transcend scales, offering insights from the nano to the metre scale, and highlights the immense potential of the nanoworld to revolutionize biomedical studies, paving the way for innovations