Yes, that is me, back in 1976. Your hair is mainly clear, and gets its color from pigments called melanins. The melanin is produced by cells called melanocytes. If your melanocytes decrease their production of melanin, your hair gets lighter, turning gray. OK, so what causes the melanocytes to stop producing? Part of it is genetic, part do to hormonal changes (which can be caused by stress), and part can also be due to diet, chemical exposure, etc. I don't worry about the gray hair, as most of mine has turned invisible instead.