Lichtenberg figures are branching electrical discharges that occur within insulating materials. They can appear on both flat and 3D surfaces and create tree-like fractal patterns.
Electrical treeing often occurs in high-voltage equipment prior to causing complete breakdown. Following these Lichtenberg figures within the insulation during post-mortem investigation of an insulation failure can be useful in finding the cause of breakdown. An experienced high-voltage engineer can see from the direction and the shape of trees and their branches where the primary cause of the breakdown was situated and possibly find the initial cause. Broken-down transformers, high-voltage cables, bushings and other equipment can usefully be investigated in this manner.
Lichtenberg figures may also appear on the skin of lightning strike victims. These are reddish, fernlike patterns that may persist for hours or days. They are also a useful indicator for medical examiners when determining the cause of death. Lichtenberg figures appearing on people are sometimes called lightning flowers, and they are thought to be caused by the rupture of capillaries under the skin due to the passage of the lightning current or the shock wave from the lightning discharge as it flashes over the skin.