Understanding the dynamic evolution of electronic and structural properties in materials is crucial for developing next-generation energy conversion technologies. This seminar focuses on our recent investigation of monolayer MoSe₂ where we probed signatures of valley polarization as a function of pump handedness. These studies were enabled by recent advancements in time-resolved anisotropic solid-state high harmonic generation (sHHG) spectroscopy developed in our group. Generally, sHHG spectroscopy is an emerging non-perturbative nonlinear optical technique (i.e., a strong field interaction rather than a multiphoton interaction) that is well poised to study transient electronic structure and symmetry in materials. In sHHG, a strong mid-infrared field drives tunnel ionization between the valence and conduction bands, intraband currents, and interband recombination, where the resulting electron trajectories imprint electronic structure information into the emission spectrum. In collaboration with theorists, we found that the resulting transient sHHG anisotropy from MoSe₂ can be ascribed to a combination of enhancement from resonant excitonic effects and depletion from carrier scattering that reduces coherence during the sHHG process. These results point to the application of time-resolved anisotropic sHHG spectroscopy in the context of quantum materials (e.g., topological insulators) for catalysis and interfacial electron transfer in van der Waals heterostructures. Furthermore, because sHHG is an all-optical technique, measurements are possible in a wide array of sample environments such as liquids and diamond anvil cells suggesting that sHHG has potential for development as a valuable tool for studying in situ electronic structure and symmetry in materials.