The magnetic field dependence of the isotropic nonrelativistic one‐electron atom with nuclear spin‐1/2, in its electronic ground state, is reviewed. Attention is called to the little‐known fact that a level crossing exists (at fieldB∼17 T for1H) between the two members of the upper spin (MS=1/2) doublet. Anisotropy of such a hydrogenic atom, due to the presence of a suitable external electric field (for instance,1H trapped in crystalline SiO2) causes anticrossing of these levels and causes previously forbidden magnetic‐dipole transitions to attain appreciable intensity in thatBregion.