First Person is a series of interviews with the first authors of a selection of papers published in Biology Open, helping early-career researchers promote themselves alongside their papers. Gregory Redpath is first author on ‘ Serotonin: an overlooked regulator of endocytosis and endosomal sorting?’, published in BiO. Gregory is a postdoc at the Lowy Cancer Research Centre, The University of New South Wales (UNSW) Kensington Campus, Sydney, Australia, investigating the regulation of endocytosis – how cells internalise what they need to function – and in particular how this ties in with serotonin and mental health.