A variety of approaches have been proposed in recent years for construction of solid optics. After a brief review of the goals and history, a new, systematic approach is described that involves the total removal of air gaps from the system. This requires 'solid air' for light propagation. Solid air, in turn, behaves differently from the more familiar air. In particular, it has a larger index of refraction and more dispersion. Modular, highly manufacturable systems approaches are described.