Cryogenic microcoolers can be used to cool small electronic devices to improve their performance. The authors present a micro-cold-stage of only 0.05 cm3 that cools to 96 K, applying Joule-Thomson expansion in a 300 nm high flow restriction. Critical in such a microcooler is the deposition of water molecules that migrate to the restriction and block the flow. Because the microcooler is made of glass the authors had the unique opportunity to monitor this phenomenon and combine this visualization with experimental data. This provides significant insight in the way this clogging develops and opens possibilities to realize stable operation.