Abstract.  The LCLS beam with its high peak brightness, short pulse duration, and tunable X-ray photon energy provides revolutionary capabilities to study the transient behavior of matter in extreme conditions. The particular strength of the Matter in Extreme Condition (MEC) instrument is to combine the unique LCLS beam with high power optical laser beams, and a suite of dedicated diagnostics tailored for this field of science (including an X-ray Thomson scattering spectrometer, an XUV spectrometer, a Fourier domain interferometer, and a VISAR system). We will present the current state of the MEC project, the scientific capabilities that the instrument brings, and a short overview of Plasma and High energy density experiments that have already been performed on FELs and are planned for the near future.