The Smart Jacket reacts at low temperatures by raising the material up to two centimetres and thereby creating a thermo effect that increases the internal jacket temperature. In contrast at high temperatures, the material shrinks all the way down to two millimetres to allow body heat to escape.. The jacket contains a micro computer that monitors the temp. Inside the jacket on different areas, the computer has a display that shows the body temp. and on the display you can program it to your most comfortable temp you wish inside the jacket ex. 22° C. then the jacket will work to keep that temp. and finds a comfortable thickness, at all times.