A fundamental cellular mechanism ensures that proteins are transported to the places they are needed in the cells. So-called vesicles are responsible for that transport. Determining their composition has been difficult up to now, not least because of their short life span. By combining innovative investigative techniques, biochemists at Heidelberg University have succeeded in analysing two of these transport vesicles – the COPI and COPII vesicles – comprehensively for the first time. The results of the research were published in the journal Cell Reports.