Soft matter self-assembly results in a variety of crystalline and quasicrystalline arrangements. These arragements may minimize the free energy, and be in thermodynamic coexistence with the liquid state. At such state points, the likelihood of finding the presence of a patch of the crystalline structure within a background liquid state is increased, which is a spatially localised state. We discuss the implications of such states for nucleation. Moreover during self-assembly, non-topological defects such as grain boundaries are common, arising from local variations of properties such as amplitude, wavelength, orientation, etc. This talk also explores the idea of treating such non-topological defects as spatially localised structures that are embedded in a background pattern.