Reconstructing metamorphic evolutions becomes increasingly difficult at high pressures and temperatures because of the effects of overprinting and the diffusional equilibration of major elements. Robust accessory minerals and slow diffusing trace elements and isotopes, which can be measured at the micro-scale, are often the key to deciphering high grade metamorphic events in these complex systems. The ultimate aim is to link trace element patterns in accessory minerals to those from rock-forming minerals critical for geothermobarometry in order to constrain P-T-time paths. In this session we invite contributions from petrology, geochemistry and geochronology that employ these tools to resolve metamorphic processes from grain to crustal scales.