Lichtenberg figure

"Lightning tree" redirects here. For the song "The Lightning Tree", see Follyfoot.
Modern 3D Lichtenberg figures or "electrical treeing" in a block of clear acrylic, created by irradiating the block with an electron beam. Actual size: 80 mm × 80 mm × 50 mm (3 in × 3 in × 2 in)
Lichtenberg figures are generated by a sliding spark discharge on the flask with a mixture of gases. Structural differences between the "positive" and "negative" figures can be observed.
Lichtenberg figures are generated by a sliding spark discharge on the flask with a mixture of gases. Structural differences between the "positive" and "negative" figures can be observed.
The slight branching redness traveling up this person's leg was created by current from a nearby lightning strike

A Lichtenberg figure (German Lichtenberg-Figur), or Lichtenberg dust figure, is a branching electric discharge that sometimes appears on the surface or in the interior of insulating materials. Lichtenberg figures are often associated with the progressive deterioration of high voltage components and equipment. The study of planar Lichtenberg figures along insulating surfaces and 3D electrical trees within insulating materials often provides engineers with valuable insights for improving the long-term reliability of high-voltage equipment. Lichtenberg figures are now known to occur on or within solids, liquids, and gases during electrical breakdown.

Lichtenberg figures are natural phenomena which exhibit fractal properties.