This book deals with the fundamental casting technology issues of how metal solidifies within a mould and of when, where and how equiaxed crystals are formed. The author describes how he discovered the phenomenon of crystal separation and established the principle of controlling cast structures, and describes the events leading up to the success of the OCC (Ohno Continuous Casting) Process which enables the continuous production of a single crystal ingot. This book will be of interest to students and researchers as well as to practising engineers.