A group of young international and very talented designers did work at a special project with metal casting called Copy nature . The results are really interesting; take a look for example at this, a Yellow and Purple combination of elements from a banana and an eggplant to form the heel of the shoe. It is cast in bronze and highly polished by designer Ninna Thorarinsdottir (Iceland - pity I could not find her web!).
See more experiments here.