The observation of protoplanetary disks at the astronomical unit scaleis one of the most exciting key programs for long baselineinterferometers. Existing observations have questioned the models ofcircumstellar environments of young stars; but this is just thebeginning. Here, to provide the reader with a sense of what can bedone today in this field, actual observations of the pre-main sequencestar FU Orionis with near-infrared interferometers IOTA and PTI arepresented. Every step, from raw data reduction to final interpretation,is described. The limits of current observations and the promise offuture contributions from the VLTI are discussed.