The hardest part about making these necklaces is finding a tiny bottle with a cork! Fortunately for all of us, the Internet makes this job a little easier. I found mine, approximately 1-inch high, at an online miniature store.
Once you have your bottle, carefully remove the cork and fill the bottle about 3/4 of the way full with your version of fairy dust. This can be glitter, seed beads, or anything else you can think of that will fit into the bottle; I prefer fine glitter. If you use glitter, it is easiest to fill the bottle if you make a funnel using a piece of paper.
Next, push the end of the headpin through the cork; push it all the way down so the hoop is touching the cork. Use a wire cutter to cut off all but about 1/4 of an inch of the end of the headpin, and bend up the end to help hold the pin in place.
Cover the sides and the bottom (the side where you folded up the end of the headpin) of the cork with glue and put it back in the bottle. Set it aside and let it dry.
If your bottle does not have a cork or you don't have headpins, you can glue a bead to the top of the bottle to cover the hole. You want to make sure the bead is not too big or too small, and you also want to make sure you glue it on sideways so you can see both holes.
Finally, once the glue is dry, you can string a chain, ribbon, piece of yarn, etc. through the hoop in the headpin to complete your necklace. You may need to use a split ring if your chain or ribbon is too wide to fit through the hoop in the headpin.