Mass photometry is a novel label-free approach that can quantify the mass of protein complexes under native-like conditions at the single-molecule level. In this webinar, Dr. Adar Sonn-Segev will present how mass photometry provides quantitative information on sample heterogeneity using minimal volumes with molecular resolution. She will discuss how this approach applies to several different workflows including chemical crosslinking and multi-step purification, comparing it to the standard tools for sample purity.