To understand the mechanisms underlying the function and dynamics of the nervous system it is essential to develop tools capable of recording and modulating a diversity of signals employed by neurons and glia. In addition to addressing the signaling complexity of the nervous system, these tools must match the mechanical and chemical properties of the neural tissue to avoid foreign body response and functional perturbation to local circuits. Our group relies on materials design to address these challenges. By leveraging fiber-drawing methods inspired by telecommunications and textile industries, we create flexible and stretchable multifunctional probes suitable for recording and stimulation of neural activity as well as delivery of drugs and genetic information into the brain and spinal cord. We use these tools to probe brain circuits involved in control of motor functions, anxiety, and fear and to promote recovery following spinal cord and peripheral nerve injury. In addition to polymer-based fibers, we develop a broad range of magnetic nanotransducers that can deliver thermal, chemical, and mechanical stimuli to neurons when exposed to externally applied magnetic fields. Magnetic nanoparticles can undergo hysteresis and dissipate heat in alternating magnetic fields. This local temperature increase can be used to directly stimulate activity of heat-sensitive neurons or to trigger release of pharmacological compounds and designer drugs from thermally responsive carriers. Similarly, magnetic nanomaterials with large magnetic moments can be employed to deliver torques when exposed to slow-varying magnetic fields. Since biological tissues exhibit negligible magnetic permeability and low conductivity, magnetic fields can penetrate deep into the body with no attenuation allowing us to apply the nanomagnetic transducers to remotely control deep brain circuits associated with reward and motivation as well as adrenal circuits involved in regulation of corticosterone and (nor)epinephrine release.