Glow in the Dark Thread
Embroidery threads.
Seriously now, no joke: these threads glow in the dark like cray-zay! A finely braided thread (meaning, it won't split like a floss, but you can stitch with it all the same) that you can mix in with your regular embroidery to give it new life when the lights go down! Super neato. Five colors, five yards (and then some) each.