Functional electrical stimulation (FES) is a rehabilitative technique where low level electrical voltages and currents are applied to an individual in order to improve or restore function lost to injury or disease. In its broadest definition, FES includes electrical stimulation technologies that, for example, are aimed at restoration of a sense of hearing for the deaf, vision for the blind, or suppression of seizures in epilepsy or tremors for people with Parkinson's disease. Most FES devices and systems are known then as “neuroprostheses” because through electrical stimulation they artificially modulate the excitability of neural tissue in order to restore function. While sometimes used synonymously with FES, the term functional neuromuscular stimulation (FNS) is most commonly used to describe only those FES technologies that are applied to the neuromuscular system in order to improve quality of life for people disabled by stroke, spinal cord injury, or other neurological conditions that result in impaired motor function (e.g., the abilities to move or breathe). Another technology closely related to FES is that of therapeutic electrical stimulation (TES), wherein electrical stimulation is applied to provide healing or recovery of tissues (e.g., muscle conditioning and strengthening, wound healing). As will be seen, some FES and FNS technologies concurrently provide or rely upon such therapeutic effects in order to successfully restore lost function. For illustrative purposes, much of this article is centered on FNS and related TES devices and technologies.