The seminar will describe the state of the art instrumentation for X-ray spectroscopy on board satellites, both present and future. It will then demonstrate some exquisite diagnostics of astrophysical plasmas. A few examples of which are electron temperature measurements of active-galaxy winds from their narrow radiative recombination continua, and the spectroscopic detection of a shock contact discontinuity in a planetary nebula based on the same spectral feature. We will then highlight absorption measurements of outflows from supermassive black holes shined on by gas falling into the black hole. These spectroscopic diagnostics have been proven useful to constrain the physics of the outflowing plasma, even when no complementary spatial information is available. Finally, some relevant laboratory experiments will be described, as well as ways to harness high quality laboratory measurements to astrophysical diagnostics.