Scientists at the Massachusetts Institute of Technology (Cambridge, MA) have developed a new technique for creating plastic foams that could be used in a wide array of medical and industrial applications (Proc. Natl. Acad. Sci. USA 97, 1970–1975, 2000). Their approach uses uniformly sized hydrocarbon particles as a template that can subsequently be removed by a solvent, leaving behind an intact polymer foam. The size and chemistry of the wax particles determines the size of the pores in the foam and the final structure of the material. To test the system, the team carved a block of foam made with a biodegradable polymer into the shape of a human nose, then seeded the block with bovine chondrocytes. After a two-week incubation in a bioreactor, sections of the artificial nose showed a stable composite made of cartilaginous tissue and biodegradable polymer. Another experiment demonstrated that an enzyme could be chemically linked to the biodegradable foam, allowing it to be slowly released in active form as the polymer breaks down. Apart from medical applications, the technique could be used to design catalyst beds and enzyme-immobilized bioreactors.