A magnetic field probe (1) having a capsule (3), in which an MR-active substance (5) is encapsulated. Two coils (7, 9) are preferably arranged in the capsule (3). Advantageous production methods for magnetic field probes (1) are also described, as well as advantageous uses of the magnetic field probe (1) and methods in which magnetic field probes (1) of this kind and arrangements of magnetic field probes (1) are used.