The technique of small-angle neutron scattering is used to study structures of size on the order of 1 nm or larger. This article briefly introduces the technique for crystalline matter, crystalline matter with imperfection, and noncrystalline matter with middle range order and the importance of the technique in materials and life science. The present status and the future plan for the technique are also presented with the idea of complimentary utilization of the technique with other scattering techniques.