This chapter provides a summary of the various material related factors that have to be taken into consideration while understanding the micro-cutting process. The material aspects of size effects in the micro cutting range from increasing in material strength at small scales, influence of phases and crystallographic planes, and the importance of fracture in promoting ductile and brittle material micro cutting. The chapter considers the basics of the stresses and strains seen in the machining process. It focuses on the plastic behaviour of materials particularly at the micro-scale highlighting differences in behaviour, which affects the micro-cutting process, compared to that at the macro scale. The chapter also considers the effect of fracture on micro-cutting process characteristics. It provides an overview of the various materials that are processed using the micro cutting process ranging from ductile metals to brittle materials and polymers.