And unlike the other gowns that will never be worn again, separate pieces from Emma's outfit can be used again.
Emma's stylist Sarah Slutsky explained everything in an Instagram post:
Tonight, the stunning @EmmaWatson on the #RedCarpet at the Met Ball in a look crafted by the incredible team at @Calvinklein. With the help of @ecoage this 5 piece look is created from 3 fabrics woven from yarns all made from recycled plastic bottles. Plastic is one of the biggest pollutants - being able to turn this waste into a high quality material is a real success story. Also this beautiful look was designed with the intention to be repurposed for future use; the pants can be worn on their own, the train can be used for another red carpet - the ultimate #30Wears! #MetGala2016 Makeup: @therealdotti Hair: @visapyyapy
The theme of this year's gala, which was held at Metropolitan Museum of Art in New York on May 2, was 'Manus x Machina: Fashion In An Age Of Technology.'