The 4th Workshop of Hydro3D (Reliable and high Productive (>80% yield) Hydrogen sensor Module based on 3D Nano-Structure Technology for High concentrated environment) related to EUREKA Network Projects will be held in BEIA Consult International, Bucharest, Romania on September 21 – 22 (Thu. – Fri.), 2023. The Hydro3D project aims to develop a hydrogen gas sensor with a micro-heater at a hydrogen-based society that is fabricated using MEMS technology. The introduction of hydrogen as a consumer fuel has caused heightened concern over its safety with a corresponding increased interest in hydrogen sensors and leak detection.