UPDATE: Attempting to create "fractal burning" in wood with microwave transformers has killed at least 34 people. It is exceptionally dangerous and should not be attempted.
Imgur user PapJ06 created these interesting Lichtenberg figures by electrocuting wood blocks with a modified microwave transformer, then applying glowing powder and resin.
Each piece is different due to variations in materials and process. Some are particularly lovely. The set includes step-by-step instructions if you'd like to try it.