Very sensitive HI absorption spectra ( \Delta \tau \sim 10 ^ { -4 } over 1 km/s ) toward high latitude QSOs have revealed a population of tiny discrete features in the diffuse ISM with peak \tau of 0.1 – 2 % and core line-widths corresponding to temperatures as low as 20 K. Imaging detections confirm linear dimensions of a few 1000 AU .
We suggest these structures may be formed by the stellar winds of intermediate mass stars .
A more speculative origin might involve molecular “ dark matter ” .