I knew those clip-on magnifiers were good for something other than soldering. That’s an 0603 surface mount LED, held down by wire glue. The traces are silver conductive ink, and those huge-looking red and black conductors are 22-gauge hookup wire. Here’s a wider view:

I like the idea of being able to work in this kind of scale for cards or origami or wearables, because with 0603 (or even 0402 for the really deft-fingered) it becomes easier to make stuff where the LEDs support the design, rather than where the point of the design is that it has LEDs in it. Tiny batteries and SOIC processor package here we come…