The chapter discusses the development and neurophysiology of mentalizing, or the ability to understand others' mental states. Mentalizing likely begins around 18 months of age, with implicit attribution of intentions and other mental states. By 4 to 6 years, explicit mentalizing becomes possible, allowing children to explain false beliefs. Neuroimaging studies in adults reveal three key components consistently activated during mentalizing tasks: the medial prefrontal cortex (MPFC), temporal poles, and posterior superior temporal sulcus (STS). These components are involved in distinguishing mental from physical states, detecting agency, and accessing social knowledge. The chapter also explores the development of mentalizing from early infancy, highlighting milestones such as the ability to understand joint attention, imitation, and the distinction between knowing and seeing. Neuroimaging studies using various tasks, such as reading stories and playing economic games, have identified these brain regions. The temporal poles are linked to generating semantic and emotional contexts, the STS to processing complex behaviors, and the MPFC to executive processes and the attitude towards sensory signals. The chapter concludes by discussing the role of early social cognition components and the importance of learning and experience in the development of mentalizing.The chapter discusses the development and neurophysiology of mentalizing, or the ability to understand others' mental states. Mentalizing likely begins around 18 months of age, with implicit attribution of intentions and other mental states. By 4 to 6 years, explicit mentalizing becomes possible, allowing children to explain false beliefs. Neuroimaging studies in adults reveal three key components consistently activated during mentalizing tasks: the medial prefrontal cortex (MPFC), temporal poles, and posterior superior temporal sulcus (STS). These components are involved in distinguishing mental from physical states, detecting agency, and accessing social knowledge. The chapter also explores the development of mentalizing from early infancy, highlighting milestones such as the ability to understand joint attention, imitation, and the distinction between knowing and seeing. Neuroimaging studies using various tasks, such as reading stories and playing economic games, have identified these brain regions. The temporal poles are linked to generating semantic and emotional contexts, the STS to processing complex behaviors, and the MPFC to executive processes and the attitude towards sensory signals. The chapter concludes by discussing the role of early social cognition components and the importance of learning and experience in the development of mentalizing.