The return to the natural structure of a protein or nucleic acid from a denatured (more random coil) state. For example, a protein may be denatured [lose its native (natural) structure] by exposure to surfactants such as SDS or to changes in the pH of the medium, etc. If the surfactant is slowly removed or the pH is slowly readjusted to the optimum for the protein, it will refold (snap) back into its original (native) form.
The reassembly of a molecule or of a molecule’s shape, e.g., the rejoining of unraveled complementary strands of DNA into a double helix.