The article reviews recent progress in high-sensitivity nanoscale nitrogen-vacancy (NV) magnetometry, highlighting the most pertinent results and future perspectives. NV centers in diamond offer unique capabilities for detecting and imaging weak magnetic fields due to their atomic-size and long spin coherence times. The review covers the principles of NV magnetometry, including the photophysics of NV defects, their use as atomic-sized magnetic sensors, and methods to improve sensitivity. It discusses experimental implementations, such as single spin scanning-probe magnetometry and ensemble magnetometry, and applications in nano magnetism, mesoscopic physics, and biology. The article also addresses critical issues like engineering NV defects near surfaces, sensitivity to temperature fluctuations, and magnetic field sign. The ultimate goal is to provide an overview of the state-of-the-art in nanoscale NV magnetometry and its potential for future advancements.The article reviews recent progress in high-sensitivity nanoscale nitrogen-vacancy (NV) magnetometry, highlighting the most pertinent results and future perspectives. NV centers in diamond offer unique capabilities for detecting and imaging weak magnetic fields due to their atomic-size and long spin coherence times. The review covers the principles of NV magnetometry, including the photophysics of NV defects, their use as atomic-sized magnetic sensors, and methods to improve sensitivity. It discusses experimental implementations, such as single spin scanning-probe magnetometry and ensemble magnetometry, and applications in nano magnetism, mesoscopic physics, and biology. The article also addresses critical issues like engineering NV defects near surfaces, sensitivity to temperature fluctuations, and magnetic field sign. The ultimate goal is to provide an overview of the state-of-the-art in nanoscale NV magnetometry and its potential for future advancements.