This article originally appeared in MindBodyGreen.

In terms of light, much of the conversation tends to focus on quantity, not quality. We know that getting some vitamin D from sunlight is crucial, and baking in the sun for ages does quite a lot of harm in the long run. But in terms of the types of light itself? You might not give it a second thought.

Well, according to New York Times bestselling author Max Lugavere, we should start using different types of light to our advantage. In fact, light is a form of readily available, no-cost medicine, and it's crucial for our sleep, cognitive function, and (as it turns out) our immune systems. But as with most aspects of well-being, it's all about balance. "Light is either a form of medicine, or it can potentially accelerate aging," he says.