Abstract : Silicon pixel detectors are beginning to be used in large particle physics experiments. The hybrid technique (detector and electronics on two separate wafers) allows large surfaces to be built. For ATLAS at LHC it is proposed to cover areas of more than 1 m2 with 5000 to 10000 pixels/cm2. Each pixel has a full electronic chain directly connected which means very low input capacitance and no integration of dark current. Furthermore, silicon strip detectors and CCD's have been successfully tested for x-ray detection. Recent results indicate that a spatial resolution in the micron range can be obtained. Building on the CCD developments, the pixel detectors are becoming the best candidate for 2-D X-ray detection, with high speed, high spatial resolution and on-chip smart readout.