Abstract: Temporal topological physics, the temporal analogue of spatial topological states of matter, reveals profound connections between momentum-band topology and temporal boundary states. This concept not only revolutionizes the paradigm of band topology but also offers new opportunities for wave manipulation in the time dimension. In this review, we introduce the fundamental concepts and recent research on temporal topological states. We mainly focus on temporal topological states in photonic time crystals with periodically modulated refractive indices, non-Hermitian systems with gain/loss, and space-time topological events formed by combining temporal and spatial topology.