Just like you can too little or too much of certain macros (carbs, protein, fats), you can get too little or too much of certain wavelengths of light (visible, infrared, UV) - Infrared is like protein, most don’t get enough - Visible (blue) is like carbs, most get too much and the low quality - UV is like fats, often demonized, but it is the wrong fat in the wrong context that is bad, just like UV Not perfect metaphor but you get the point