<p>The inversion of left and right in the mirror image of a human body is accounted for by the different sensitivity of optics to shape and functionality, and, in the general case, by the elementary properties of vector spaces. The observation that some objects give a mirror image that is not superposable on the object itself is extended to the existence of pairs of <i>real</i> objects, each superposable on the mirror image of the other. The components of such pairs, called enantiomorphs, are distinguished as right- and left-handed. The property that allows this distinction is chirality, which is relevant in both contact and field interactions with chiral counterparts. Chirality may be present both locally and for the whole object, at both macroscopic and microscopic scales; in the latter case, chiral molecules, ions, radicals – distinguished through their representations <i>–</i> are called enantiomers. In both domains, the chirality of an object is related to its use, but it may be vital for pharmaceuticals and phytosanitary products at the molecular scale, because the enzymes, sensors, and receptors of living organisms are, as a rule, chiral, and therefore recognize – and subsequently process for often necessary functions – only one of the possible enantiomers. Chirality is an observable that cannot modify the chemical potentials, which are physical quantities determining the equilibrium constant of chemical reactions. Thus the reactivity of enantiomers can differ only in terms of kinetics.</p>