Perlite is a naturally occurring volcanic glass that is expanded by heating. When heated to high temperatures, it expands to many times its original size, creating lightweight, porous granules. This unique structure makes perlite an excellent material for improving soil aeration and drainage, which is beneficial for plant growth. In gardening and horticulture, perlite is often mixed with soil to enhance its properties. It helps retain moisture while preventing compaction, allowing roots to access air and water more easily. Additionally, perlite is sterile and free from pests, making it a popular choice for starting seeds and growing various plants.