A seal which is reputed to be the pinnacle of chakra control. By storing a vast amounts of chakra over an extended period of time into a specific point on their body — usually the forehead — the user creates this seal, which manifests in the form of a rhombus-like marking. Once the seal is formed, the user's already impressive chakra control allows them to perform techniques without any wasted energy. When released, the seal will either spread across the user's face or wrap around their entire body. The stored chakra is then released into their body, greatly amplifying the power of their techniques.
When written as '白毫', byakugō means 'Ūrṇā' (Literally meaning: Fine White Hair), which is a white swirl of fine hair on the forehead of the Buddha, represented in art by a spiral or a dot, or even a gem or pearl. It represents the third eye which allows one to see past the mundane world and into the divine world.
Tsunade also uses a portion of the seal's chakra to maintain her youthful appearance.