Perlite & Vermiculite
Perlite and Vermiculite are used to add air and moisture to your root zone. Perlite is for providing extra air and the vermiculite will retain moisture. These two mediums are also good for cuttings and seeds when combined in a 50/50 ratio.
Perlite is a mined mineral and is a form of volcanic glass when super heated it pops like popcorn creating a large irregular granule that has great qualities when used as a hydroponic medium, its pH stable, its porous structure is great at holding oxygen, and dries out quickly.
Perlite can be used on its own but is more commonly mixed with coco coir or soil so add extra aeration and drainage. Vermiculite is another mined material. In looks like mica rock, but when super heated it expands to 10 times its original size.
Vermiculite can hold moisture of around 200 to 300 times its weight, this means vermiculite retains too much water to be used by itself, as it will suffocate the roots of plants, most growers mix it with perlite to achieve an ideal medium.