When objects appear different in the mirror, scientists call them chiral. The behavior of many familiar objects, from molecules to elementary particles, depends on which mirror-image version we interact with. Perhaps Looking-glass milk isn’t good to drink,” she says. Pasteur found that, while they contain all the same components, the mirror versions of chiral molecules can serve distinct chemical functions. While either version can be synthesized, the sugars produced and consumed by living organisms are always the right-handed ones.