Matter is composed of atoms and molecules. Atoms in themselves are composed of tiny particles, including electrons. As illustrated in Figure 5.1, these electrons not only revolve around a nucleus but also spin about their own axis. The orbiting and spinning electrons are considered to be tiny current loops. The two loops with Iorb and Ispin currents encompassing infinitesimal surface areas Sorb and Sspin result in two magnetic dipole moments morb (= Iorb Sorb) and mspin (= Ispin Sspin). As is evident from Table 5.1, in all major magnetic materials, the contribution of spinning electrons is more prominent than that of revolving electrons; thus, its influence on the magnetic property is more significant.