Tiny drops of oil can be arranged to write information and read it back remotely, described in this 2014 paper. The oils suspended in water, literally colloids can be written to or read from using both optical and electronic mechanisms. When written to, the information is stored by rearranging the stable pattern of the droplets within a larger grouping. The applications of this technology include mixing the substance into batches of other goods as a marker, high density memory (estimated in the range of terabytes per gram), or memory for nano machines (still being much too large for than application, but showing promise).
Usefully, the structures assemble themselves under the right conditions lending themselves to industrial application.