I often catch myself marveling at how much I’ve changed since childhood. Back then, I was a tiny person with a round face, soft skin, and a rather squeaky voice. Now, my reflection in the mirror is taller, older, and definitely carrying more wrinkles than I ever imagined. Sometimes, it feels like my entire body is brand new. I’ve heard that every cell in our system gets replaced over time, which makes me wonder: if I’m made of different parts than I was decades ago, am I really the same perso...