House-warming effect leads to enormously increasing number of people who suffer from skin cancer. And the main cause of skin cancer is improper exposure of skin areas to sunshine. Studies show that the risk of skin cancer doubles if you’ve had 5+ sunburns. Although SPF & PA is usually indicated on the product , it is still hard for people to know when to reapply sunscreen. So people tend to reapply sunscreen late or even forget about it, which would lead to sunburn,suntan,and even skin cancer. “Sun Stamp” is a bottle designed of sunscreen. There is photochromic stamp on top of the sunscreen bottle cap with the bottom layer for sunscreen storage. Simply stamp on your arm. Then apply sunscreen, covering the stamp pattern. The black stamp pattern would turned red as the sunscreen absorbs the UV light and runs low. It would serves the reminder for people to know when exactly to reapply sunscreen.