 So now we're going to talk about the process of vision, which after all of the light gets to the back of the retina and activates the photoreceptor, a lot of people are confused about what happens next. How is that photoreceptor activated? How do I get action potentials? So that's what we're going to show you with a simple demonstration that you can do at home. Okay? So if you pretend that you are the opsin protein within a cone, pro-photoreceptor, okay? The opsin protein is going to have a little niche for a derivative of vitamin A called retinol. That retinol is going to fit right into the niche that's in the opsin protein, okay? When the light comes into the eye and goes all the way back to the photoreceptor, the energy of the light itself is going to cause the retinol to straighten. And when it straightens, it no longer fits inside of the niche that it had, meaning that that retinol is going to leave. This process is called bleaching. At that point, that's what stimulates the production of action potentials. But you have to reform your opsin. You can't just leave it empty. So the enzyme is going to come through and it's going to regenerate that retinol protein so that, or the retinol, so that it fits back inside the opsin protein, okay? And now it's ready for more light energy. So it happens so quick you don't even know because of the fact that you see in color. So when the light comes in, it causes the bent cis retinol to straighten, becomes a trans retinol, which doesn't fit in the niche. So it bleaches, you get action potentials, regenerate, fits back in. So it's straighten, bleach, regenerate, fit.