Please note that this is the Narutopedia's article on the anime and manga ninjutsu used by Deidara. If you are looking for the article on the video game technique used by Deidara then you should head to Ultimate Art.
The highest form of Deidara's explosive clay (his "Ultimate Art" (究極芸術, Kyūkyoku Geijutsu)), C0 is a suicide-bomb technique used as a last resort. Deidara reveals a mouth on his chest, which is stitched up. After undoing the stitches, Deidara feeds it a large ball of clay. The mouth on his chest has a direct connection to his heart so a large amount of chakra is built up. It then kneads chakra directly from the meridians of the heart and keeps doing it without interruption until the moment of the explosion. His explosive chakra then manifests itself in his veins, flowing through his body. These "veins" then condense into a sphere that slowly cracks open and detonates, producing a unique explosion that covers a ten kilometre blast radius.