This book presents a comprehensive and holistic study of microstrucure evoution during solidification and additive manufacturin.g Bulk metallic glasses and their composites have attracted a lot of attention lately in the scientific community owing to their excellent mechanical properties (combination of hardness, strength, and high elastic strain limit). However, they still lack toughness and tensile ductility and exhibit catastrophic failure upon tension. This can be overcome by various means, of which in situ introduction of ductile crystalline precipitates/phases during solidification proved to be the best. Various studies have been carried out in the last two decades, which explain this phenomenon. However, there is a gap on how this can be achieved in modern additive manufacturing exploiting inherent nature of process. This book aims to bridge this gap. A comprehensive and holistic study is presented, documenting the step-by-step evolution of these materials since their inception till date, explaining the development of toughness in them by modeling and simulation of microstructure evolution during solidification and additive manufacturing.