This paper presents a novel method for nanoscale imaging and magnetometry using diamond spins under ambient conditions. Traditional optical microscopy and magnetic resonance imaging (MRI) have limitations in resolving molecular-scale structures, but the sensitivity of MRI can overcome these barriers. The authors demonstrate that single-electron spin states can be detected optically at room temperature by using magneto-optical spin detection. Specifically, they show how to determine the location of a spin associated with a single nitrogen-vacancy (NV) center in diamond with nanometer resolution. By placing these NV spins in functionalized diamond nanocrystals, biologically specific magnetofluorescent spin markers can be produced. The technique achieves nanometer-scale resolution without probes located closer than typical cell dimensions. Additionally, a single diamond spin can be used as a scanning probe magnetometer to map nanoscale magnetic field variations. The potential impact of this room-temperature single-spin imaging is significant, as it could enable the probing of biologically relevant spins in living cells. The paper also discusses the energy level scheme and structure of the NV defect, the detection of single spins, and the experimental setup for gradient imaging and scanning probe magnetometry.This paper presents a novel method for nanoscale imaging and magnetometry using diamond spins under ambient conditions. Traditional optical microscopy and magnetic resonance imaging (MRI) have limitations in resolving molecular-scale structures, but the sensitivity of MRI can overcome these barriers. The authors demonstrate that single-electron spin states can be detected optically at room temperature by using magneto-optical spin detection. Specifically, they show how to determine the location of a spin associated with a single nitrogen-vacancy (NV) center in diamond with nanometer resolution. By placing these NV spins in functionalized diamond nanocrystals, biologically specific magnetofluorescent spin markers can be produced. The technique achieves nanometer-scale resolution without probes located closer than typical cell dimensions. Additionally, a single diamond spin can be used as a scanning probe magnetometer to map nanoscale magnetic field variations. The potential impact of this room-temperature single-spin imaging is significant, as it could enable the probing of biologically relevant spins in living cells. The paper also discusses the energy level scheme and structure of the NV defect, the detection of single spins, and the experimental setup for gradient imaging and scanning probe magnetometry.