Bose Gases with Nonzero Spin

Gaseous Bose-Einstein condensates with nonzero spin feature multicomponent order parameters that reflect the internal degrees of freedom. They exhibit a rich variety of superfluid and magnetic phenomena similar or complementary to those of superfluid helium-3. The unprecedented degree of manipulability of atomic gases makes spinor condensates a unique playground for exploring symmetry breaking, topological excitations, and the interplay between superfluidity and magnetism. An overview of these subjects is provided.