Natasha Russian Doll Ring by nOir Jewelry - Babushka ring inspired by the Matryoshka Russian doll. And yes it actually opens up and there is a smaller doll inside. Ring measures 1 inch wide by 1 inch long, 1 inches in height.
Anatomical Heart Locket, by Peggy Skemp. An anatomically correct heart necklace that even has the correct chambers of the heart on the inside. If it wasn't so damn expensive, I would buy this in an instant.