Quick Illuminated Boxes
Dia 
Adding A Light
To illuminate the boxes, we're going to use something commonly called a 'throwie'. To make one, slide an LED onto a battery so that the two legs straddle it. The LED is polarized. Make sure you attach it to the battery with the correct orientation. The long leg should be on the positive (+) side of the battery, the side with writing stamped onto it, and the short leg should be on the negative (-), textured side. Don't worry if you put it on backwards the first time.
Wrap a piece of tape around the legs and the battery to secure it in place.
Tape the throwie inside your box, and the light will shine through the holes, illuminating your design and making the box look absolutely magical!
The box is meant to be disposable, as favor boxes generally are, so eventually the battery will die. Before that happens, though, you'll get days of light out of it! I recommend rigging these up the day of your event. They'll shine their brightest, and the recipients will have a lovely glow to remember you by for days after you give them their boxes!