Each
phase (i.e.
liquid,
solid etc.) of physical
matter comes to an end at a transitional point, or spatial interface, called a
phase boundary, due to the
immiscibility of said matter with the matter on the other side of said boundary. This immiscibility is due to at least one difference between the two substances' corresponding physical properties. The behavior of phase boundaries has been a developing subject of interest and an active research field, called interface science, in
physics and
mathematics for almost two centuries, due partly to phase boundaries naturally arising in many physical processes, such as the
capillarity effect, the growth of
grain boundaries, the physics of
binary alloys, and the formation of
snow flakes.