Artist Brian Baity carves breathtakingly intricate designs out of eggshells. He has posted a few finished eggshell designs on Instructables, as well as some notes (in the comments) on how he makes them, as he describes here:
I went though a stage where my goal was to remove as much material from an egg shell as possible while still retaining the shape and image of the egg. Carving an egg shell like this is great fun and watching people’s reactions when they seem something like this is even more fascinating.
– Book Dissections by Brian Dettmer