Ultrafast electron microscopy (UEM) has emerged as a powerful characterization technique that integrates ultrafast laser technology with electron microscopy. It encompasses a range of modalities, including ultrafast transmission electron microscopy (UTEM), scanning ultrafast electron microscopy (SUEM), and ultrafast cathodoluminescence (U-CL). These techniques enable the direct tracking of nonequilibrium dynamics with femtosecond temporal resolution and atomic-to-nanoscale spatial resolution, offering unprecedented insight into the microscopic mechanisms of light–matter interactions. Based on the photon pump–electron probe scheme, UEM allows precise control of the time delay between laser and electron pulses, thereby facilitating real-time observation of ultrafast processes such as carrier relaxation, lattice vibrations, structural phase transitions, and magnetic domain evolution. To date, UEM has been successfully applied to a wide range of systems, including two-dimensional materials, semiconductor devices, catalytic materials, magnetic materials, and biological macromolecules. These studies have significantly advanced the understanding of nonequilibrium phenomena in materials and provided critical support for the design and optimization of next-generation functional materials and devices. With ongoing improvements in electron sources and detection systems, the spatiotemporal resolution of UEM continues to advance, demonstrating great potential for probing ultrafast processes at the atomic scale and driving breakthroughs in condensed matter physics, materials science, and information science.