Netsuke are miniature Japanese sculptures which are most often carved from ivory or wood, and sometimes from other materials. They were first made in the early 17th century, and used to fasten a small box (the inro) containing medicines and personal belongings to the sash (or obi) worn around traditional Japanese garments such as the kimono. Later on they were made solely for ornamental purposes.
The ivory skull and wooden mask netsuke shown in the photograph above are on display at the Victoria and Albert Museum in London, which has a very nice collection of these delightful objects. Despite being just 1.5 inches in height, they are exquisitely detailed. The skull, for example, is anatomically accurate, with the mandible, maxilla, and frontal, nasal and zygomatic bones depicted correctly.