Aeroponic systems aren’t seen very often, but basically the principle of this technique is when the plants are suspending from some form of attachment and the root systems are misted or watered with nutrient solution.
It goes to prove that plants can be grown without any media, so long as they have some form of support to hold them upright.
As shown below the plants are suspended by a hook from an overhead endless chain which rotates and at intervals passes each plant through a nutrient spray chamber.