When we stay out in the sun for too long, its harmful ultraviolet rays penetrate through our skin cells and damage their DNA and RNA. To protect excessive damage to the skin, our body’s natural effect is to produce melanin which creates a barrier between the sun rays and our skin and also naturally darkens it. The more time in the outdoors we spend, the more melanin is produced. This forms layers on the skin and is what we usually see as a tan.