Sunflowers belong to the family Asteraceae, also know by the older name Compositae. What appears to be a single flower, is actually a composite of smaller flowers. The petals of a sunflower head are actually individual flowers called ray flowers. The central disk is made of smaller individual flowers called disc flowers. The flowers around the outer edge open and mature first folowed by a progressive wave of opening of the disc flowers that moves toward the center. In the movie shown here, the progressive opening of the disc flowers is seen. The movie was shot over a period of about three days.