This chapter reviews the basic properties of some new laser crystals and describes new developments in the field of rare earth and transition metal solid-state lasers. The progress in the area of diode pumped lasers has contributed very much to the renaissance in the field of solid-state lasers. With diode laser pumping it is possible to obtain higher efficiencies and to build rigid all solid-state devices with simpler and more compact design. Compact solid-state lasers in the visible spectral region are of potential interest, especially for display and high-density optical data storage applications. An alternative approach presents generation of visible laser radiation by up-conversion schemes, which incorporate energy transfer processes or two step pump processes as ground state and excited state absorption. Electric dipole transitions within the 4f shell are parity forbidden and admixtures of wavefunctions with opposite parity are necessary to create weak transition probabilities.