This chapter provides an in-depth introduction to the UNDAC concept, its core activities, and its integral role in international emergency response efforts. It delves into the fundamental principles guiding UNDAC operations, including preparedness missions, standard Terms of Reference, and generic mission objectives. Additionally, it elucidates the methodology employed by UNDAC teams, detailing their composition, team membership, functions, and requisite qualifications. Furthermore, the chapter highlights the comprehensive support network available to UNDAC, encompassing operational partners and support services essential for effective mission implementation.