"Chakra is the molding of the physical energy present in every cell of the body and the spiritual energy gained from exercise and experience."
Minato returned to his natural form and held up his hand, focusing his chakra into a very small ball of blue chakra. The Rasengan in it's smallest, easiest to control form wasn't much int he way of a weapon, not yet. But it was still energy and powerful and he was careful to keep that little ball well under control or they might both find themselves on their backs.
"Shinobi train to use their chakra in many different ways. As weapons or as healers."