Stars realize a variety of physical conditions inaccessible in the lab. Various stages of stellar evolution are influenced by microphysical processes that are sensitive to the fundamental properties of elementary particles. This makes it possible to use them as particle physics laboratories. Until recently, stars of 5-10 solar masses were not considered particularly useful for particle physics. I will discuss how the evolution of these stars can be qualitatively changed by neutrino magnetic moments or axion emission. In particular, the mere existence of Cepheid variable stars turns out to provide world’s best bound on the axion-photon coupling in a broad range of parameters.