The process and science of machining is introduced here. Machining is a versatile process widely used in the manufacturing industry to process raw materials of various types to impart shape and finish to products. While typically used as a secondary shaping process (primary shaping being done using casting, forming, etc.), it is also often used as an all-in-one primary process for prototyping. By its very nature machining process removes unwanted material to effect the shaping and surface generation. The nature of this material separation and its consequences are discussed in this chapter. Energy is needed for such material, and some fundamental aspects of how to provide the needed energy for causing the material removal are also discussed. The reader will obtain a basic intuitive idea of why the machining processes remove material in a typical fashion generating so-called chips, and the factors that affect the quality of the shape and surface generated will be highlighted. Some basic nomenclature of the process and cutting tools are used to quantify the deformation involved in machining and show the process mechanics. Experimental techniques used to study this process and some research trends in machining are also shown towards the end of this chapter. © Springer-Verlag London 2015. All rights reserved.