The early 1990's heralded the deployment of vastly improved space instruments in the ultraviolet (HST) and X-ray (ROSAT) bands, where thermal inhomogeneities in high-excitation chromospheres and coronae are seen in their most favorable light. The infrared spectrum provides a key complementary view of inhomogeneities, but only recently has begun to be seriously exploited for studies of the solar chromosphere and the outer atmospheres of other late-type stars.