This chapter examines the formation of a second-order process zone around a defect. The nature of this defect we do not specify in advance. The aim is to understand the phenomenon’s most universal and general aspects. The focus is particularly on a zone where the daughter phase is embedded in the matrix of the bulk mother phase, as well as the reverse situation where the bulk daughter phase hosts the mother-phase process zone (Boulbitch 1992, Boulbitch and Korzhenevskii 2016).