So these thick filaments basically wrap around one another, or these myosin wrap around one another to form our thick filament. And on the edges, at the end of each of these thick filaments, we basically have extensions known as myosin heads. And these myosin heads, as we'll see in the next lecture, are basically responsible for actually binding and interacting with our thin filaments. So these heads are shown on this diagram, and these heads are responsible for interacting with the black region that thin filament. And that's exactly what causes that contraction. These myosin heads pull on our actin and that basically causes that contraction as we'll see in the next lecture.