An hourglass is a device used to measure time, typically consisting of two glass bulbs connected by a narrow neck. Sand or another granular material flows from the upper bulb to the lower one, taking a specific amount of time to do so. Hourglasses can vary in size and duration, with some designed to measure just a few minutes and others lasting for hours. Historically, hourglasses were popular before the invention of mechanical clocks. They were often used in various settings, including kitchens for cooking and ships for navigation. Today, hourglasses are sometimes used as decorative items or in games to create time limits.