Sunflowers, members of the Asteraceae family, are actually made of hundreds of tiny flowers, not just one large one. The center of a sunflower is packed with tiny flowers called disc florets, seen here. The “petals” around the edge of the sunflower head (the whole thing is called an inflorescence) are called ray florets. [x]

Fun fact: The small florets on a sunflower head follow the pattern of a fibonacci spiral. The fibonacci sequence is a mathematical sequence in which you add the new number to the one before, starting with 0 and 1.
(0, 1, 1, 2, 3, 5, 8, 13, 21…) 

A sunflower in my garden.

Photo by me. 

The sunflower is a member of the plant family Asteraceae, or Compositae. Asters are remarkable for their type of inflorescence, which is a head of florets. What this means is that what we consider to be the “flower” of the sunflower is actually made up of lots and lots of little flowers, called florets. The center, darker florets are disc florets, while the outer, petal-like ones are ray florets.
Sunflower seeds are indehiscent achenes.