Board Thread:General Discussion/@comment-26304307-20150426194028/@comment-28584561-20150428110625

That's the power of immortality having an effect on mortal cells. Steven's Gem powers causes his cells to either regress back or progress further, making him virtuallly immortal, so long as he thinks like anyone not in the brink of death. Theoritically, as long as Steven thinks as a child, his cells will never age, ergo he will never age. But seeing that Steven, like any other human, is subjected to maturation on a psychological level, he will continue to age physically in tandem with his state of mind.