Using surface x-ray diffraction (SXRD) we study the atomic structure of clean and adorbate covered topological insulators. In combination with spin polarized angular resolved photoemission (Tusche) and ab-initio calculations (Theory department) we focus on the relation between surface and electronic structure. As an example, the figure shows the model of the near surface structure of a (0001) oriented bulk Bi₂Se₃ crystal. We find significant vertical relaxations between the topmost atomic layers as well as between the first van der Waals gaps.