This project performs optical nano-imaging and -spectroscopy with newly developed ultrafast, coherent, and nano-cavity enhanced modalities, to resolve the coupled intra- and interlayer quantum dynamics in 2D semiconductors and their heterostructures on the nanoscale. Many of the exotic properties of 2D quantum materials and their heterostructures emerge from coupling between tunable degrees of freedom including choice of material, layer stacking and relative orientation, electric gating, doping, or strain. However, understanding and controlling the interplay of the different intra- and interlayer interactions that gives rise to the rich electronic, optical, spin, and other properties has remained a major experimental challenge. In order to address these problems, ultrafast coherent, pump-probe, and nano-cavity enhanced spectroscopy and -imaging are applied. These techniques allow for the selective excitation and modification of one or more of the resonance excitations to distinguish between coupled internal parameters and resolve their relative contributions to the overall material response that are difficult or impossible to separate otherwise. The goal of the proposed work is the study of electronic, photonic, phononic, and spin properties of transition metal dichalcogenide monolayer and heterostructures. In nano-spectroscopic imaging of the intrinsic materials properties through extrinsic nano-optical control, and the ultrafast spatio-spectral-temporal nano-imaging, their coherent and incoherent quantum dynamics will be resolved with nanometer spatial and femtosecond to nanosecond temporal resolution. Resolving competing relaxation pathways and their coherent dynamics of intra- and interlayer and both spin- and momentum- forbidden dark excitons, their sensitivity with respect to defects, strain, layer stacking, twist angle, and localization associated with defects and Moiré superlattices, will inform a more targeted sample fabrication to achieve optical devices of high quality for heterostructure photonics, or provide the basis to realize the hypothesized applications of Moiré-excitons for quantum emitters arrays or twistronics. This research project will provide foundational knowledge for the development of 2D quantum materials for semiconducting devices, or in opto-electronics for light emission and detection. Further, these precision measurements with spin selectivity and single photon sensitivity informs in quantum information science from spin switching based gates and memories to entangled photons and quantum sensing.