Abstract: More than one decade ago, evidence for multiple stellar populations was found in old globular clusters. Interestingly, recent work has shown that young and intermediate-age star clusters may not follow challenge popular scenarios that aim to explain the origin of multiple stellar populations in star clusters. In this talk, I will review the topic of multiple stellar population in star clusters and describe efforts understand the “not-so-simple” stellar populations in relatively young star clusters. I will attempt to draw some conclusions from these studies and summarise where we stand in this active area of research.