The mutation occurs when the child in the embryo stage absorbs a small portion of the life-force of their mother's tailed beast or traces of it that is buried in their mother or father's chakra that originate from the tailed beast of a jinchūriki ancestor. Once absorbed, the embryo makes the life-force their own by getting rid of their old life-force. This completely alters their physiology and in some cases appearance, giving them the abilities and traits Children of Chakra are known for.