Localization of functional fails in ICs makes use of physical interactions that the devices produce under electrical operation. The focus is on electroluminescence (keyword: photon emission) and signal responses to stimulation by scanned beams of laser light or particles. In modem chip technologies access of this information is only available through chip backside. This paradigm shift requires a full revision of chip analysis techniques and processes. This has also been a kick-off of a rush in development of new methodologies. Here, an overview is given which parameters are crucial for successful analysis techniques of the future and how photon emission, laser based techniques and new preparation techniques based on focused ion beam (FIB) open the path into this direction. (c) 2005 Published by Elsevier B.V.