An EBIT can selectively create, in principle, any charge state of every naturally occurring element, has good control on atomic collision processes, and can produce nearly ideal conditions for the analysis of highly ionized plasmas of astrophysical importance. A microcalorimeter enables the broadband detection of x-ray emission with high energy resolution and near-unity quantum efficiency in the energy range wherein many cosmic x-ray sources emit the bulk of their energy (0.2 keV–10 keV). The combination (EBIT+ microcalorimeter) provides a powerful tool for laboratory studies of the atomic/plasma processes underlying the energy release mechanisms in cosmic x-ray sources. We briefly describe some early experiments with a microcalorimeter built by the Smithsonian Astrophysical Observatory (SAO) and deployed on the NIST EBIT. We also present some very recent observations with a more advanced microcalorimeter built by SAO that can obtain an energy resolution of 4.5 eV. The higher spectral quality produced by the new system will be useful in laboratory measurements of interest in x-ray astronomy.