How do actin filaments form?

Actin filament is formed by the assembly of identical actin monomers called globular-actin (g-actin). During the assembly, g-actin monomers are arranged in long spiral polymer strands. Two strands twist around each other in a double helix conformation to form an actin filament. The g-actin monomers occur at repeat distances of about 36 nm.