Nanotechnology is a novel tool for handling of matter at the microscopic level, within the atomic, molecular, and supramolecular domains. While neuroscience and neuroengineering operate at the cellular level, their association with the nanotechnology is bringing synergic unexpected strides. In the last decade, an unprecedented increase in the successful application of nanotechnology methods to basic neuroscience and to clinical practice occurred. Novel nanotechnologies are expected to bring important insights into brain mechanisms and medical care to patients. The chapter details attempt from different disciplines to improve brain performance in both healthy people and patients who suffer from neurological disabilities. Applications of nanotechnology (with the advent of nanoparticles, nanowires, carbon nanotubes, devices, sensors, interfaces) are employed to augment, invasive/noninvasive record, stimulate, repair, cure, or regenerate the brain functions (sensory, motor/locomotor, cognitive/memory/learning, reward/emotion) and brain circuitry (in cortex, subcortex/basal ganglia/thalamus, brainstem, spinal cord).