This document discusses smart textiles, which integrate microelectronics into textiles to endow them with new properties and active behaviors. Smart textiles can sense and react to stimuli in their environment. They are categorized as passive, active, or ultra smart depending on their sensing and response capabilities. The key functions of smart textiles are sensing, data processing, actuation, storage, and communication. Examples of smart textile applications discussed include thermoregulating materials, chromic materials, luminescent materials, conductive materials, voltaic materials, and electronic textiles. Areas of further research include sensors, actuators, signal transmission and control systems, and integrated textile processes.