Enantiomers of chiral molecules are non-superposable mirror images with the same structural formula. In achiral environments, enantiomers have identical physical and chemical properties, and this prevents separation by classical methods. For example, crystallization and filtration (separation by solubility), distillation (separation by boiling point) and standard achiral chromatography (separation by interaction with a stationary phase and a solvent) are unable to resolve enantiomers.