What you'll need:
Take your glass and fill it with vinegar (we used a tumbler). Add the egg and let it sit for 24 hours. It starts to bubble and move a around. I left it on the kitchen table so Evie could watch it.
After 24 hours, take the egg out and wash it off a bit. The shell will have started to come off but needs to sit for a while longer. So fill your glass again and put the egg back in.
After this time, take the egg out, wash it off and it's like a ball! You can see the yolk floating around in there and it's bouncy (but very fragile, Evie dropped it and it still broke, but really good to look at).
We had so much fun with this. Letting her watch it and touch it while it was working its magic in the vinegar was very cool and when it was all said and done and she could play with it and hold it was really fun for her, especially being able to see the yolk move around!
We used a brown egg and I wonder if we used a white egg if it would be even more clear, we'll have to check it out!