Cays are small islands found in tropical regions around the world. They are also known by other names, including islets, atolls, keys, rock piles and reefs. These names are used interchangeably depending on location and geological characteristics. Cays are usually formed by the accumulation of sand, coral and other debris over a long period, which is then compacted to create a solid landmass. Some cays are home to unique species of plants and animals, making them popular tourist destinations for snorkelling and diving. Despite being small in size, cays play an important role in the ecosystem and contribute to the overall biodiversity of the region they are found in.