Plique-à-Jour

Plique-à-jour enameling adds color to this beautiful butterfly brooch
Photo courtesy of Scott Papper, GIA GG, AJP, CM (NAJA), Global Gemology & Appraisals
Plique-à-jour is an enameling technique where translucent enamel is applied in unbacked cells, allowing light to pass though.

Plique-à-jour is French for "letting in daylight".