Now on top of this actin protein found inside our thin filament, the thin filament also consists of two other proteins. We have a protein known as troponin, and we have tropomycin. And these two proteins are involved in muscle contraction, as we'll see in the next lecture. So this is our diagram of the thin filament. So if we zoom in on these horizontal black regions, we basically get the following diagram. We have these individual spherical actin monomers that basically join together to form our polymers.