This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.This article contains the results of investigating the gas-dynamic structure of supersonic underexpanded axisymmetric microjets of nitrogen flowing from sound nozzles with a diameter of 10 ÷ 340 μm. The length of the supersonic part of the jet significantly increases together with a decrease in nozzle diameter starting from the size 23 μm. Measurement results are compared with known data obtained for macro- and microjets
