An outbreak of infections with the mpox virus – formerly known as monkeypox – in Europe in 2022 led to a rise in interest in poxviruses. An international research team investigated the structure of the poxvirus prototype, the vaccinia virus (VACV). The team found that trimers of the A10 protein, an abundant protein of the virus, play an important role in the formation of the mature virus. These trimers may also be involved in interactions with other cell components during infection, which could provide a starting point for the development of antiviral therapies against viruses from the poxvirus family.