The user can activate cells within an organism's body, increasing the speed of cellular functions, increasing physical attributes such as speed and healing, or maybe accelerating them with enough speed and energy to produce heat, destroying them. It can also be used offensively on targets by causing unnatural cell activation, causing cancer. The activation of cells can cause a temporary optimization, making the affected looking younger.
Taisuke Kanō (Alive: The Final Evolution) using his Destruction and Rebirth to activate cells, either regenerating or destroying them, with the side effect of generating heat and fire due to cell acceleration.
Taisuke Kanō's (Alive: The Final Evolution) power of Destruction and Rebirth explained in detail by Yūta Takizawa.
Kyoko Kirisaki (Black Cat) using her Tao power, Heat, which is a basic application of using one's ki to accelerate cell function, increasing her bodily temperature.
Aoba Takatsu's subordinates (Code:Breaker) possess the ability Cell Stimulation, which causes their cells to grow and regenerate whenever they are attacked, gaining in size and power as long as not all of their cells are destroyed at once.
Lucy (Elfen Lied) using her vectors to stimulate Kouta's cells, healing his mortal wounds.
Tsunade (Naruto) using Creation Rebirth to activate her cellular division via releasing the tremendous amounts of chakra she stored up, regenerating all injuries and lost limbs, at the cost of her lifespan.
Tsunade (Naruto) preparing the Cell Activation Technique to activate all the cells in Lee's body, to restore his body even during a life-risking operation, increasing his survival chances during the more invasive and delicate procedures.
Kabuto Yakushi (Naruto) using Yin Healing Wound Destruction to activate cells around his wounded area, reconstructing cells and able to keep specimens alive longer than normally feasible.
Kabuto Yakushi (Naruto) using the Mystical Palm Technique to inject medical chakra into his patient, which speeds up the body's natural healing process via cell acceleration. This does not regrow lost limbs, but simply closes wounds to staunch blood loss.
Users of the Sun Flame (Reborn!) can use its Activation function to induce and improve cellular activity.