Two weeks ago, during the inaugural Tokyo Hotaru festival, 100,000 little balls with LEDs were released in the Sumida River. The impressive installation was made to resemble fireflies (hotaru) and looked like a blur on the river when viewed from a distance. The spheres were 100% powered by solar energy and lighted up upon contact with water. After floating through central Tokyo, the LED’s were caught by a large net.

Photos: Mai Suzuki, Jeremy V, ajpscs | Source: