 van ’t Hoff and Le Bel provided no account of the mechanism by which chiral molecules affect the rotation of plane polarized light (Needham 2004). But by the end of the century, spatial structure was being put to use in explaining the aspects of the reactivity and stability of organic compounds with Viktor Meyer’s (1848–1897) conception of steric hindrance and Adolf von Baeyer’s (1835–1917) conception of internal molecular strain (Ramberg 2003).