Rockwool is made from molten rock spun into cotton candy-like fibers and then compressed into cubes, blocks, or slabs. The purpose is to support the requirement of the plant in the different plant stages. These cubes allow for better absorbency of nutrients. Seedlings started in cubes are easily transferred to blocks and then onto slabs, if desired. Seedlings or cuttings started in cubes can be transplanted into more traditional planters and growing mediums.