An overview is given of recent studies of crystal nucleation and growth in silicate and phosphate based glasses, emphasising microstructural characterisation. The following topics are discussed: nucleation kinetics in silicate systems, comparisons with classical theory, and new evidence in the early stages of crystallisation of Li₂O · 2SiO₂ glass for the appearance of previously unreported metastable precursor phases, probably crystalline polymorphs of lithium disilicate; the role of P₂O₅ as a nucleating agent in lithia—silica glasses; volume nucleation and glass ceramic formation in CaOP₂O₅ based glasses, particularly the roles of additions of Al₂O₃. TiO₂, SiO₂ and B₂O₃; crystallisation of aluminosilicate glasses including celsian and barium osumilite compositions, and marked differences in crystallisation between melt-derived and sol—gel derived compositions.