A method and system are described for gathering information about an object including single domain particles comprising iron oxide and having a diameter in the range of about 5 nm to 80 nm. The method for gathering information comprises generation of a static magnetic field of less than about 0.1 Tesla applied to the object and generation of an RF energy, transmitted as a continuous wave, at a frequency so as to generate electron paramagnetic resonance of the single domain particles. The method also comprises detecting the electron paramagnetic resonance of the single domain particles in the form of an image of the object.
