  We review the properties of quarkonia under strong magnetic fields. The main
phenomena are (i) mixing between different spin eigenstates, (ii) quark Landau
levels and deformation of wave function, (iii) modification of $\bar{Q}Q$
potential, and (iv) the motional Stark effect. For theoretical approaches, we
review (i) constituent quark models, (ii) effective Lagrangians, (iii) QCD sum
rules, and (iv) holographic approaches.
