In this chapter, we focus on the properties of process zones in cases where the mother-to-daughter phase transition is of the first order, commonly referred to as first-order zones. The bifurcation that initiates the formation of these first-order zones is invariably hard. We begin by introducing a concept we call “quasi-second-order process zones.” In these zones, bifurcation theory remains applicable even in the face of hard transformation in those regions of the parametric space where the amplitude of the order parameter is small. Without specifying the generating potential, we offer a comprehensive solution that describes these quasi-second-order process zones and exposes their universal properties. Moving on from the small amplitude scenario, we turn our attention to a more general case. Here, we derive estimates for the zone’s emergence temperature, its size, and its interface’s thickness. The chapter concludes with the proof of a theorem stating that the size of the zone grows infinitely as the temperature approaches the bulk binodal (Boulbitch and Toledano 1999, Boulbitch and Korzhenevskii 2020).