Observations of molecules and dust in supernova SN 1987a and SN 1995ad are summarised and the inferred masses of CO and SiO are presented. The chemistry is used to argue that macroscopic mixing occurred in which the interpenetrating clumps in the ejecta retained their microscopic integrity. An explanation of the anomalous temperature structure is advanced. Molecular candidates for some of the unidentified spectral features are proposed.