"When lightning flashes across the sky, you only get a chance to glimpse its fractal form for a split second. But when you send 15,000 volts coursing through plywood, you get a much better look at how it grows. Melanie Hoff, a student at the Pratt Institute in New York City did just that, and the result is a timelapse where you can see the patterns slowly grow out and smolder, like lightning made from molasses."
That's the description that introduces the 15,000 Volts video on YouTube. On her own Vimeo Channel, Hoff adds a few more details about what you're seeing above, saying "Yes, the grain of the wood influences the pattern and the direction [it takes]. The layers of veneer and the glue that holds them together causes the growth to progress much slower than in non-plywood. This is sped up hundreds of thousands of times" in the timelapse film. The musical accompaniment is "Aire De Zamba," by Augustin Barrios Mangore.