Ultrafast electronic dynamics are foundational to a wide range of chemical processes. For example, charge transfer and relaxation, crucial processes implicated in the function of photovoltaic and photocatalytic materials, are driven by electron motions and their interactions with electromagnetic fields. Research efforts in the Li group focus on the development of time-dependent many-electron theories and computational methods to investigate these ultrafast non-equilibrium dynamical processes and their manifestations in spectroscopic probes. This talk will illustrate the power of quantum electron dynamics and time-dependent electronic structure theory by presenting several important applications in molecular and materials sciences.