Villin is a fast-folding protein and has a unique hydrophobic core at the center in its folded form. In the present study, the folding process of Villin was investigated with parallel cascade selection molecular dynamics (PaCS-MD). Our computational results show that formation of the central hydrophobic core was a rate-limiting step in the folding process. In more detail, the folding is regulated with a gathering of four PHE residues to form the hydrophobic core.