Why does shining a laser on an IC locate a short? How can the source of an excess time delay in a digital circuit be determined? There has been an explosive expansion of laser based FA techniques in the last decade, each with their own catchy acronym, e.g. LADA, RDL, OBIRCH, and TIVA. Surprisingly, the underlying physics of these four examples is all the same. This tutorial will explore the fundamental interaction of laser beams with semiconductors and then expand these fundamentals into practical examples. The goal is to demystify laser based FA techniques, to supply the attendee with a basis for interpreting test results and to motivate development of new test approaches to fit the specific failure under investigation.