Butene

But-2-enes are the simplest alkenes that show E/Z isomerism. In one isomer, the terminal carbons sit on the same side of the double bond; in the other, they sit on opposite sides. Their boiling points lie so close together that separating the two is virtually impossible, yet their physical properties are similar enough that rigorous separation is rarely necessary.

In this pair of earrings, each side stands for one isomer. The two pieces share the same components arranged in mirrored ways, just as the molecules themselves do, a wearable expression of the quiet difference between cis and trans.