If you're a woman who feels wired but exhausted, foggy by mid-afternoon, and completely depleted by evening — there's a piece of your biology that rarely gets discussed, and it starts with light. Here's the mechanism: Inside nearly every cell in your body are mitochondria — tiny structures that turn the food you eat and the oxygen you breathe into usable energy. When your mitochondria are producing energy efficiently, you feel clear, capable, and steady. When they're not, you feel exactly the way so many women describe to me: depleted in a way that no amount of coffee or discipline seems to fix. What most people don't realize is how much your mitochondria depend on timing. Your body runs on a circadian rhythm — an internal clock set primarily by light. When morning sunlight reaches your eyes, it signals that clock to align your cortisol, your metabolism, and your cellular energy production for the day ahead. That same signal, hours later, helps set you up for the deep, restorative sleep where your mitochondria actually repair and rebuild. Skip the light, blur the timing, and the whole system drifts. Energy production falters. Sleep suffers. The fatigue and brain fog compound. And a standard lab panel will often tell you everything looks "normal." It isn't that nothing is wrong. It's that your body is asking for an input it hasn't been receiving. The encouraging part: light, timing, and circadian alignment are among the most accessible levers we have — and the science behind them is genuinely compelling. I experienced this firsthand working 24-hour-long shifts mostly in an operating room lit by LED, which doesn't provide our bodies with the biological signals they rely on. I'm teaching a workshop on exactly this — sunlight, mitochondrial health, energy production, and circadian rhythm — in my next women's group call on September 22 at 5 PM. If you'd like to join us, send me a message, and I'll share the link.