Three dimensions are necessary before chiral symmetry can come into play. Molecules that are composed of four or more atoms may possess chirality, meaning that the same arrangements of the positions of the components of the molecule can be achieved in two different ways, one being the precise mirror image of the other. In chemistry this is important, since any given chiral molecule will act differently depending on the chirality of the partner in a reaction. In other words chemical reactions do not favor one chirality over another. Its mirror image is a left-handed screw.
Complex molecules can exist in the two forms, one looking like the mirror image of the other.
If they are in a liquid, tumbling around arbitrarily, they will still affect light traveling through the liquid and in fact plane polarized light may have the axis of its polarization rotated by the action of these molecules. If the right-handed and the left handed molecules are equally represented, there will be no net effect. However, if one type predominates over the other, then there will be an effect, which is in practice often readily observable. It is in liquids that this type of observation is important, because there is no long-range effect that would cause many of one kind to dominate over the optical path. A non-racemic liquid then requires an explanation for the preference of one sense of chirality over the other.