Optically active spin - defects in wide band gap materials have gained significant interest in the recent years . Precise control of spin at the single defect level has led to potential applications ranging from quantum information processing to nanoscale sensing. In this presentation, I will focus on the most promising candidate in this family of paramagnetic defects – nitrogen vacancy (NV) center in diamond. I will describe the physics behind the extraordinary properties of NV centers and will briefly review the recent progress in this field. Subsequently, I will discuss my contribution that includes exploration of charge dynamics in diamond, utilization of charge-state as a probe to spin-state, sensing of the paramagnetic environment, and investigation of efficient polarization transfer mechanisms.