Skyrme model is among the simplest extensions of chiral effective theory including anomaly. We investigate how an external magnetic field deforms the classical Skyrmion soliton structure while maintaining the topological winding. We further identify quantized Skyrmions as neutrons and protons, revealing a mass split between them induced by the magnetic field. More intriguing aspects arise when we annex multiple Skyrmions to form a crystal and realize the ¥pi^0 domain wall as a special class of solution. We establish the thermodynamics and phase diagram of different classes of Skyrme crystals, beneath which is the topological transmutation between ¥pi_3(S^3) and ¥pi_1(S^1).