Water microdrops of about 50 microm in diameter, generated by an ink-jet system, have been used to hydrate fragments of Pogonophora tubes. In situ X-ray microdiffraction with a beam size of 10 microm was used to follow the structural transformations that affected the crystalline beta-chitin part of the specimens. Starting from anhydrous chitin, the formation of a full beta-chitin dihydrate was observed within about 90 s. A disordered intermediate phase with variable d-spacing that could be due to a mixture of anhydrous and hydrated beta-chitin layers was also detected.