Pick up your shrink plastic and draw your bone. Anatomy book will give you a good knowledge of all kind of human parts. If bones do nothing for you, go for any internal organ.
Draw very detailed and realistic looking picture to shrink plastic sheat and your jewellery will be fabulous! (if freehand drawing is not your cuppa-tea, you can always draw is straight out from the book or copy picture to desirable size and trace bigger image to your plastic sheet)

Cut you desing - dont forget to make holes for the chain!
Then bake your desing, please follow the instructions for shrink plastic you are using

Gather all the equipments you will need.

Add the chain to your desing. Then cut the chain to desired lenght and add the clasp.

Congratulete yourself, you jewellery is now done and ready to be used.

It is time to enjoy!