An important accessory for the well-dressed.
Netsuke (net-skae) are devices to hold the sash of a kimono in place, or to attach a purse or some other small object to the sash.
Netsuke are normally carved out of rare woods or semiprecious stones. They can take myriad forms, varying from fancy buttons to animal shapes, human figures and fantastic creatures.
It is fairly safe to say that netsuke are far more important to Japanese culture than their nearest Western analogues (tie clasps and cuff links) are to Western culture. Their importance in advertising a person's status (or desired status), or a facet of personality, goes beyond any purely functional purpose.
Aside from functionality, many netsuke are quite elaborate and beautiful. Some are quite ancient, having been handed down through the centuries and family heirlooms or as power gifts. Netsuke carving is a unique art form; the character of an individual netsuke or the fame of the artist who created it contributes far more to its value than does the material it is made from.
As one might expect, many people find netsuke interesting to collect. There is a booming trade in the little things both in Japan and in the West. However, I expect that the most important netsuke are the ones kept in one's family.