Finnish design studio Aivan, along with scientists from the VTT Technical Research Center of Finland and Aalto University, have built the first pair of headphones grown by fungi, yeasts and microbes. 
They’re called Korvaa and they’re just a non working prototype, designed and built with the intention of proving the potential of synthetic biology (“synbio”) in bulding a complex object made of a large variety of parts and materials. 

The frame of the Korvaa headphones was 3D-printed with a polymer “grown” by the polylactic acid of common baker’s yeast. The over-ear pads are the work of a fungus that grows cells into the air, thus creating a foamy composite that researchers mix with cellulose to stabilize its structure. There’s even a material obtained by a spider-silk-based protein, used to create the mesh that covers the speakers. 
The remaining parts are mostly built with special cellulose, grown faster in the lab by microbes, and a cellulose-mycelium composite.