The astronomical X-ray and EUV satellites of the past generally had low enough spectral resolution that atomic data of modest quality was sufficient for most interpretation of the data. Typical proportional counter resolution Δ E/E ~ 1 permits a determination of the spectral shape sufficient for an estimate of the temperature of the emitting gas, but only the Fe K feature at 6.7 keV stands out as a distinct emission line. The higher spectral resolution Einstein Transmission Grating, Solid State Spectrometer, and Focal Plane Crystal Spectrometer instruments measured a score of emission lines or line blends, permitting determinations of the elemental abundances, temperature, and ionization state of the emitting gas. The higher spectral resolution and throughput of the BBXRT aboard the ASTRO mission and the instruments planned for EUVE, ASTRO-D, AXAF, and XMM will make possible a far more detailed analysis of the data. It should be possible to derive better abundances for more elements, accurate temperature distributions, electron densities, and accurate ionization states.