Krsna appears in this material world in His original eternal form, with two hands, holding a flute. He appears exactly in His eternal body, uncontaminated by this material world. Although He appears in the same transcendental body and is Lord of the universe, it still appears that He takes His birth like an ordinary living entity. And although His body does not deteriorate like a material body, it still appears that Lord Krsna grows from childhood to boyhood and from boyhood to youth. But astonishingly enough He never ages beyond youth. At the time of the Battle of Kuruksetra, He had many grandchildren at home; or, in other words, He had sufficiently aged by material calculations. Still He looked just like a young man twenty or twenty-five years old. We never see a picture of Krsna in old age because He never grows old like us, although He is the oldest person in the whole creation — past, present, and future. Neither His body nor His intelligence ever deteriorates or changes. Therefore, it is clear that in spite of His being in the material world, He is the same unborn, eternal form of bliss and knowledge, changeless in His transcendental body and intelligence.
>>> Ref. VedaBase => Bg 4.6