10 Interesting Facts You're too Lazy to Google Pt. 2

10. Why do common household items like shampoo have expiration dates? The expiration date represents the time a product is stable based on the company's tests. The products that are past that date would still work, though not as effectively. Eating food items that are past their expiration date, however, is a bad idea. https://en.wikipedia.org/wiki/Shelf_life 9. What causes birthmarks? Pigmented birthmarks, like moles and Mongolian spots, occur due to an excess of melanin, the pigment that gives color to our skin, hair, and eyes. Vascular birthmarks, which are red birthmarks that look like port wine stains, occur due to excess blood vessels. https://en.wikipedia.org/wiki/Birthmark 8. Almost 80% of Earth's atmosphere is nitrogen. What is its purpose? Here's what happens during the nitrogen cycle.