Single-crystal architectures in glass, formed by a solid-solid transformation via laser heating, are novel solids with a rotating lattice. To understand the process of lattice formation that proceeds via crystal growth, we have observed in situ Sb 2 S 3 crystal formation under X-ray irradiation with simultaneous Laue micro X-ray diffraction (μXRD) pattern collection. By translating the sample with respect to the beam, we form rotating lattice single (RLS) crystal lines with a consistently linear relationship between the rotation angle and distance from nucleation site. The lines begin with a seed crystal, followed by a transition region comprising of sub-grain or very similarly oriented grains, followed by the presence of a rotating lattice single crystal of unrestricted length. The results demonstrate that the primary cause of lattice rotation within RLS crystals is the densification accompanying the glass → crystal transformation, rather than stresses produced from the difference in thermal expansion coefficient of the two phases or paraelectric → ferroelectric transition during cooling to ambient temperature.