A process for connecting two bodies forming parts of an electromechanical, fluid and optical microsystem, wherein a welding region is formed on a first body; an electrically conductive region and a spacing region are formed on a second body; the spacing region extends near the electrically conductive region and has a second height smaller than said first height. One of the first and second bodies is turned upside down on the other, and the two bodies are welded together by causing the electrically conductive region to melt so that it adheres to the welding region and collapses until its height becomes equal to that of the spacing region. Thereby it is possible to seal active parts or micromechanical structures with respect to the outside world, self-align the two bodies during bonding, obtain an electrical connection between the two bodies, and optically align two optical structures formed on the two bodies.