Stretchable electronics entails an intrinsically stretchable conductor. For optoelectronic devices, visual transparency of the conductor is also required. I will present the synthesis of polymer composite conductors based on silver nanowires or carbon nanotubes exhibiting high transparency, low sheet resistance, and low surface roughness. The mechanical properties of the composite electrodes are determined by the polymer matrix employed, and ranges from being rigid to flexible and elastomeric. Self-healing has also been demonstrated using a Diels-Alder cycloaddition polymer as the matrix. The composite electrodes have been used to demonstrate stretchable transparent Joule heating, pressure sensing, large-strain actuation, polymer light emitting didoes and solar cells.