The Power of Optical IR Interferometry: Recent Scientific Results and 2nd Generation Instrumentation : Proceedings of the ESO Workshop held in Garching Germany 4 8 April 2005 Celebrating the completion of the first phase of VLTI development the ESO workshop The Power of Optical IR Interferometry held in 2005 gathered researchers together to review and discuss not just interferometers but also how science uses interferometers and their impact on astronomy as a whole. This volume contains the proceedings of this workshop serving as a reference for astronomers working with optical and infrared interferometry.