Instantly Joel reverted to his new normal size, then immediately he began to get younger. He shrank and youthened, his muscles and size all melting away until he was an ordinary, skinny ten-year old. But this was only the start. Immediately his muscles began to swell again, growing to gymnast proportions, and then into bodybuilder proportions where he had it stop, standing on the line between lean and bulky. To fully enjoy the changes he wished away his clothes, and stood there about 5'4'', a foot taller than most ten year olds.
Next he began to increase the size of his genitals. But not only were they growing, they were maturing, and by the time he reached about eight inches flaccid they actually had pubic hair. And then from there he began to grow his whole body, getting larger and larger until he stood six-feet tall. This was just one experiment, and he was wondering if he could continue further.