This disclosure presents systems for x-ray illumination that have an x-ray brightness several orders of magnitude greater than existing x-ray technologies. These may therefore useful for applications such as trace element detection or for micro-focus fluorescence analysis. The higher brightness is achieved in part by using designs for x-ray targets that comprise a number of microstructures of one or more selected x-ray generating materials fabricated in close thermal contact with a substrate having high thermal conductivity. This allows for bombardment of the targets with higher electron density or higher energy electrons, which leads to greater x-ray flux. The high brightness/high flux x-ray source may then be coupled to an x-ray optical system, which can collect and focus the high flux x-rays to spots that can be as small as one micron, leading to high flux density.