And these individual actin monomers basically join together and combine to form a polymer, a long chain of actin. And two of these actin polymers basically intertwine with one another and form a helical structure that creates our thin filament. So the thin filament consists of two long polymers and these polymers consist of our actin molecule, the actin protein. 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.