Shadow Clone Technique

The Shadow Clone Technique is a technique developed by the Second Hokage: Tobirama Senju.

Overview
Similar to the basic Clone Technique, this technique creates copies of the user. However, these clones are corporeal instead of illusions. The user's chakra is evenly distributed among every clone, giving each clone an equal fraction of the user's overall power. The clones are capable of performing techniques on their own and can even bleed, but will usually disperse after hit by a strong enough force. The clones can also disperse on their own or be dispelled by the user of the technique. Shadow clones can't be distinguished from the actual person even by dōjutsu because the clones have the exact same amount of chakra as the original, and aren't made from any other substance like water clones are for example. Shadow clones also seem to be able to think for themselves and feel the original's pain to some extent, as evidenced by Naruto's clones feeling pain when the Nine-Tails' cloak awakened while he and Kakashi were fighting Deidara.

Usage
Because of the manner in which the clones are created, the user must divide their chakra among the clones, potentially using up all their chakra fairly quickly if the user is low on chakra, or makes too many clones. This is especially problematic when the Multiple Shadow Clone Technique is used; whereas the normal version will only create a few clones, the Multiple Shadow Clone Technique can create hundreds.

A characteristic that is unique to the Shadow Clone Technique is that any experience the clones gain during their existence is transferred to the user once they are dispersed. This makes the technique ideal for spying, since the user can simply send a clone to spy on a target, then have the clone disperse itself without returning, to pass the information back to the user. Similarly, because they are clones of the original, any chakra that the clone possesses will return to the original after being dispelled. Conversely, the reverse is also true and the original is still able to manipulate the chakra of the clones.

It's also useful for training purposes, since the total amount of experience the user gains is multiplied by the total number of clones being used to train. For example, if a user creates one shadow clone and trains together with this clone for one hour, then dispels the clone, the user gains two hours of training in one hour by adding the hours of clone and the user together. This particular feature is not revealed until Part II by Kakashi Hatake. When done with several hundred, like Naruto does, training that could take weeks or months can be completed in a few hours. While the technique can be extremely beneficial, attempting to use multiple clones for training purposes can be mentally harmful to the user, as not only is all the experience collected by the user, but so is all the mental stress from training each clone. Kakashi stated that Naruto is the only person able to can do this type of training, due to the amount of chakra that Naruto has.

Trivia

 * In Naruto episode 129, Sasuke Uchiha claims that the Sharingan can distinguish clones from the original. This contradicts the manga and other anime episodes.
 * An ostrich named Condor appears in the anime using this technique, but in reality it was just other ostriches.