Modern electrochemistry contributes significantly to the field of Micro-System-Technologies (MST). MST is the base of the global information and communication technology (ICT) driving most aspects of modern life. MST includes Micro and Nano scale manufacturing disciplines such as microelectronics, micro electro mechanical systems, microelectro-optics, microfluidics and more. MST, since its conception, involved many aspects of applied electrochemistry: process modules (i. e. deposition, etching, cleaning etc.), devices (i. e. biosensing, chemical sensing etc.), and energy components (i. e. sources, energy harvesting, storage etc.). We present a brief historical overview, followed by a discussion about the main topic of this work, electrochemistry and MST. To highlight the electrochemistry contribution, two examples are presented demonstrating when electrochemistry provided critical micro technologies. The first is Very Large-Scale Integration copper metallization, which is already in mass production, and the second is 3D integration of circuits and systems, which is under intense research and development.