Coconut coir growing medium comes from the coconut's fibrous husk (known as coir) that is bound together by lignin (known as pith).  With the addition of water, coir expands to an easy to work with growing medium. The addition of water increases the volume 3 to 9 times, depending on the packaging of products. This process results in a 100% biodegradable growing medium, making it a natural and safe growth medium of choice for growers

Helpful article: Using Coconut Coir for Seed Starting