The nanocomposite nature of the extracellular matrix may have been under-appreciated in the engineering of complex and functional tissues for organ transplantation, indicates a Review in this week’s Nature Nanotechnology. 　　　　Until recently, tissue construction has placed emphasis on improving mass transfer into the core of the material and designing biocompatible and biodegradable scaffolds with suitable mechanical properties. Although these are important factors, Robert Langer and colleagues suggest that the approach fails to recapitulate the cell microenvironment and the finer details of the natural extracellular matrix that regulates essential functions of the cell. 　　　　The authors set out design considerations for different types of tissues and explain how existing nanotechnological tools can be used to recreate the important nanoscale features of the matrix to enhance tissue organization and the impact of nanostructures on these artificial matrices.