A solution saturated with respect to hemihydrate is supersaturated with respect to gypsum.
But the condition of supersaturation is not sufficient cause for a system to begin crystallizing
[10]. Before crystals can grow a number of minute solid objects must exist. These minute solid
objects are called seeds, embryos or nuclei. A stable nuclei is necessary for the growth into
crystals of visible size. A stable nuclei is a particle larger than the critical size formed in a supersaturated
or supercooled system