Shape Transformation (translation meaning "Keitai Henka") is an advanced form of chakra control and a technique that is pivotal for the manipulation of chakra and the creation of new jutsu. It involves changing the form and movement of chakra, determining the size, range, and purpose of a jutsu.
The ultimate examples of shape manipulation is the Rasengan, invented by the Fourth Hokage, Minato Namikaze, which is described as shape manipulation that has been taken "to the highest possible level" and the Reikiku, invented by the Founding First Hokage, Hanaku Senju, which is described as shape gathering that has to take "to the spiritual point". The Rasengan and Reikiku relies heavily on chakra control and does not require the use of hand signs. By building up on precepts learned from the Tree Climbing Practice and Water Surface Walking Practice chakra control exercises, the Rasengan is chakra that has been rotated and then compressed into the shape of a sphere. Jinchuriki, when transforming through their progressive forms into their tailed beast, have their chakra moulded around them to resemble the shape of their tailed beast. Through further transformations, the tailed beast chakra can materialise into the flesh and bone of the tailed beast.
Combining with Nature Transformation
Shape Transformation is one of two necessary techniques for creating or modifying a technique with its counterpart being Nature Transformation. While Shape Transformation changes the form and movement of chakra, Nature Transformation changes the actual nature of the chakra, altering its properties and characteristics. Because of this, a technique like the Rasengan can be turned into the Wind Style: Rasengan or Wind Style: Rasenshuriken. The cutting nature of Wind Style, combined with the spiralling movement of chakra, can change the chakra into millions of minuscule blades in a spiralling formation