We are witnessing a revolution in which quantum phenomena are being harnessed for next-generation technology. A central challenge in this effort is to gain detailed insights in the behaviors of electrons and spins in quantum materials. In this context, quantum sensing technology realized with nitrogen vacancy (NV) center in diamond has emerged as a powerful probe of advanced materials and devices. Due to its ability to sense magnetic field with high spatial resolution over wide temperature and dynamic range, NV sensors enable the exploration of condensed matter phenomena in parameter space inaccessible to existing probes. In this talk, I will discuss our application of NV quantum sensing technology to study correlated electronic and spin phenomena. We have directly imaged, for the first time, the viscous Poiseuille flow of the Dirac fluid in neutral graphene, a finding that holds implication for other strongly correlated electrons such as those in high-Tc superconductors. Enabled by the NV platform, we have developed new capabilities for probing coherent spin-waves, which can be applied to study novel magnetic materials and spintronic devices, and a tool for charactering low-dimensional high-Tc cuprates without electrical contacts. Looking forward, I will highlight opportunities for advancing the frontiers of quantum materials and quantum technology enabled by NVs and other solid-state atomic qubits.