In this webinar, Selgar Henkel-Heinecke (Leipzig University) describes how he and colleagues used mass photometry to determine the composition of this complexmass photometry, to measure the stoichiometry of two miniature Cas12f1 ribonucleoprotein complexes, AsCas12f1 and SpCas12f1 in vitro, as well as their interaction with nucleic acids that are involved in the genome editing process.