Reproductive meristems, emerging after the transition from vegetative to reproductive development (the flowering transition), generate floral organs and other meristems, thereby impacting the inflorescence architecture and numbers and arrangement of floral organs. In this chapter, we provide a comprehensive overview of the intricate process of the formation of reproductive meristems, including the inflorescence meristem (IM) and floral meristem (FM), and the function of FM in producing floral organ primordia. The IM is formed from the conversion of the shoot apical meristem (SAM), as a consequence of the flowering transition, and then generates multiple FMs, from which floral organ primordia are derived. We outline the regulation of IM formation by multiple pathways, such as floral repression, autonomous promotion, vernalization, photoperiod, and gibberellin signaling, as well as the TFL1 gene. We then highlight the genes specifying FM identity and the genetic regulation of FM determinacy. Finally, we discuss the molecular mechanisms underlying the maintenance of reproductive meristem identities, the control of meristem growth and size, and the determination of floral organ numbers.