Eyelids are thin folds of skin that cover and protect the eyes. They help keep the eyes moist by spreading tears across the surface and prevent foreign objects from entering. Eyelids also play a crucial role in regulating light exposure, closing during bright conditions or when we sleep. Each eyelid contains muscles that allow them to open and close. The upper eyelid is typically larger and more mobile than the lower eyelid. Eyelids are lined with a delicate membrane called the conjunctiva, which helps keep the eyes lubricated and free from infection.