Magmas are subject to a series of processes that lead to their differentiation during transfer through and storage within the Earth's crust. The depths and mechanisms of differentiation, the crustal contribution to magma generation through wall-rock assimilation, the rates and timescales of magma generation, transfer and storage, and how these link to the thermal state of the crust are subject to vivid debate and controversy. This volume presents a collection of research articles that provide a balanced overview of the diverse approaches available to elucidate these topics, and includes both theoretical models and case studies. By integrating petrological, geochemical and geophysical approaches, it provides new insights to the subject of magmatic processes operating within the Earth's crust, and reveals important links between subsurface processes and volcanism.