Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) are essential tools for both the physical and life sciences, but these techniques have been limited to the detection of large ensembles of spins. By manipulating and measuring the nitrogen-vacancy centers in nanodiamonds, this invention enables magnetic resonance imaging with single nuclear spin sensitivity, in ambient conditions, at angstrom resolution. Not only can individual molecules and proteins be probed, but the magnetic fields of emerging complex materials such as superconductors can be better understood and engineered.