COMSOL ® so�ware was used to create a model of 3D fused silica microstructures. This model was converted into an input file for 3D prin�ng, adjus�ng hatching, slicing, laser power, and scan speeds using DeScribe so�ware (Nanoscribe GmbH). The object was then printed with the NanoWrite so�ware (Nanoscribe GmbH) on a 2PP lithography system (Photonic Professional GT2, Nanoscribe GmbH). First, GP-silica resin was drop-casted from the cartridge onto a silica substrate. Polymeriza�on was ini�ated by a pulsed femtosecond fiber laser at 780 nm. During the prin�ng process, laser power and laser scanning speeds were set at 40 mW and 100 mm s -1 , respec�vely. In the development step, the excess resin was removed by keeping the substrates in methanol for 10 min, and in isopropanol for another 1 min. Thermal post-processing (debinding and sintering) was conducted by hea�ng from room temperature to consecu�ve holding temperatures at rates of 1 °C min -1 . Holding temperatures where 90 °C, 150°C, 230 °C, 280 °C, 600 °C, 1000 °C and 1100 °C, at which the object was held isothermally for 180 min, 180 min, 180 min, 180 min, 120 min, 500 min and 180 min, respec�vely. Final cooling was done at a rate of 2 °C min -1 . This procedure yielded microstructures, ataining 3D resolu�on in the range of tens of micrometers and surface roughness of 6 nm. It is worth no�ng that the heat treatment steps affected the structures, and some defects can be observed (e.g., in Figure ). The final prin�ng quality can most probably be improved by adjus�ng the treatment parameters, which was, however, not in the scope of this study.