This paper is focused on the dynamics of cloud cavitation at Sub-millimeter scales, between 0.1 and 10 mm. A simple flow configuration consisting in a small diameter jet impacting a wall at 90° and then flowing radially between two plates is used. Cavitation is obtained in the gap between the two plates, due to the local flow acceleration. The scale of the setup was changed by varying separately the gap between the two plates, and the nozzle diameter. Observations were performed from the transparent bottom plate, using a high-speed camera and intense illumination, for various Reynolds and cavitation numbers. The analysis is focused on the variations of the cavity length and the Strouhal number based on the characteristic frequency of the flow instability.