abstract: Systems comprised by several interacting components may exhibit, in the thermodynamic limit, a time-periodic behavior in the evolution of their law. We have made an attempt to understand which factors may produce this phenomenon: they include noise, time-symmetry breaking, loss of Markovianity. We will first review some examples of mean field dynamics for which the thermodynamic limit can be explicitly computed and analyzed. In the second part of the talk we focus on recent partial results concerning the emergence of pulsing behavior due to loss of Markovianity. Joint work with Marco Formentin and Guglielmo Pelino