This paper reports a new technique called "micro-brush" for easy mechanical attachment and electrical interconnection between two parts. Each of the two parts can be either a single die or a full wafer. They can be attached together in selected areas containing the "micro-brushe" by simply "pressing" them together. Each micro-brush is a large array of hair-like high-aspect-ratio metal posts. When pressed together, these metal posts bend and get engaged with others from the opposite side, creating a permanent electrical and mechanical contact, all done at room temperature. High-aspect-ratio arrays of metal posts are fabricated with an areal density of ∼ 2,700,000 per cm2. The metal posts can be optionally coated with solder. Test structures have been fabricated and demonstrated mechanical and electrical attachment.