Residual thermal stresses due to thermal expansion mismatch at dissimilar material interfaces can cause serious problems in the current bonding technology, yet this is an unavoidable consequence as long as the interfaces are fabricated at elevated temperatures. An innovative solution to this problem is that the materials be bonded without applying heat, i.e., bonding at room temperature. A new technique to join two dissimilar materials, “Surface Activated Bonding (SAB)”, has been recently developed. The basic concept underlying this technique is that two atomically clean solid surfaces under contact develop a strong adhesive force. We have recently demonstrated that this method works on various materials systems, including Al2O3, A1N, SiC and Si3N4, on which polycrystalline aluminum is bonded at room temperature. In this paper, we will describe: What is “Surface Activated Bonding”? What are the electronic and chemical driving factors for bonding? Complementary experimental and theoretical studies in elucidating the fundamental aspects of the SAB will be described.