Before the field of electro-optics can realize its potential in the applied world, practical sources and detectors are needed which cover the important spectral ranges. For applications involving either ambient thermal emissions or remote chemical analysis, high brightness sources are needed in the 2 - 15.5μm range. Over the last five years, several very promising techniques have been developed for generating solid-state mid-IR sources. Important advances in nonlinear materials have dramatically improved the efficiency and reliability of the frequency down-conversion approach to mid-IR sources. Also parallel efforts to develop direct solid-state mid-IR laser have begun to bear fruit. Room temperature mid-IR lasers have been demonstrated using both cascaded quantum well materials and low phonon rare earth doped materials. While potentially simple and compact, the development of solid-state mid-IR lasers poses a number of difficult material problems. The papers in this issue of Optics Express were invited to present recent progress on materials intended for direct emission in the mid-IR.