On the quest for high sensitivity x-ray phase-contrast imaging, we fabricated the first 200 nm period hard x-ray gratings and performed the first phase-contrast imaging experiments with such high density gratings in the world. We also proposed a new way of doing x-ray microscopy which is particularly suitable for biological samples and identified molecular probes for this technology. We invented a method to speed up x-ray phase-contrast imaging which is a significant challenge for clinical applications of this technology.