Telescope Technique

By peering into a crystal ball, the user can see the current activities of anyone whose chakra signature they know. Users can view subjects from any location, regardless of distance or potential obstructions, making it ideal for intelligence gathering. The Third Hokage uses this technique to monitor the villagers of Konohagakure and thus maintain public order.

Trivia

 * In "Road to Naruto the Movie" (and its anime adaptation), Tobi used this technique to gather information for his Limited Tsukuyomi. He then used the crystal ball itself as a medium to cast and host the Genjutsu World he created with that information.
 * In Naruto Shippūden: Kizuna Drive, Gensui used this technique to control his false tailed beasts and to shoot spheres of energy.