The Constellation-X mission is a high through-put X-ray facility, emphasizing observations at high spectral resolution (Delta E/E 300 to 3000) while covering a broad energy band up to 60 keV. Constellation-X is the x-ray astronomy equivalent of large ground-based optical telescopes such as the Keck and the VLT, complementing the high spatial resolution capabilities of Chandra. Constellation-X will obtain precise measures of the chemical composition and physical conditions of objects ranging from the closest stars to the most distant quasars via x-ray spectroscopy of unprecedented sensitivity. With these capabilities Constellation-X will test GR using x-rays emitted close to the event horizon of black holes, measure dark energy parameters and observe the formation of the largest structures in the universe(clusters of galaxies), probe the intermediate redshift universe (black holes, galaxies, and clusters with redshifts in the range 0.5-4), trace the spatial distribution of "missing" baryons and dark matter in the warm intergalactic medium, study the atmospheres of neutron stars and white dwarfs, and observe the formation of metals (C to Zn) in supernovae and their ejection into interstellar and intergalactic space. Constellation-X is a key element in NASA's Beyond Einstein Initiative. We will provide an update on the status of the program, and we will discuss Con-X in relation to the XEUS mission currently under study by ESA and JAXA.