So the QRS complex is when our bicuspid and tricuspid valves close, but the T wave is when these two valves right here actually close. Now, what about this last wave we call the U wave. So the U wave is usually a very small peaked wave that follows our T wave. And what we believe the U wave actually describes is the repolarization of all the cells found within the wall separating our two ventricles. So this wall is known as our interventricular wall. And what the uWave is believed to describe is the repolarization of all the cells found within this particular segment.