Many small active molecules in cosmetics are "chiral molecules," including common ones like Ergothioneine, Ectoin, 3-O-Ethyl Ascorbic Acid, and Ceramide 3.

There are two methods for representing chiral compounds. The first is configuration representation, mainly including: ① D/L relative configuration method, and ② R/S absolute configuration labeling method. The second is optical activity representation: clockwise rotation is denoted as d- or (+)-, counterclockwise rotation as l- or (-)-, racemic mixture as dl- or (±)-, and meso compounds as meso-.

There is no fixed relationship between configuration and optical rotation direction. The D configuration might be either dextrorotatory or levorotatory.