Catheters play a key role in diagnostic and therapeutic medicine. Nowhere is this more apparent than in the specialty of interventional cardiology which is dedicated to catheter-based treatment of cardiovascular diseases. The tools of an interventional cardiologist include a variety of developed and emerging imaging technologies to guide therapy. This talk will focus not only on the science and engineering but also the on art of intracoronary imaging catheters. Intravascular ultrasound and optical coherence tomography catheter systems will serve as examples.