Aeroponics is a way of growing plants without soil and with very little water. This sounds a bit strange, but it's a very effective and efficient way of growing a wide variety of plants. Using this method means you can grow vertically as well as horizontally, so it can be a great way of saving space. NASA even did some experiments in space and found that the Asian bean seedlings they grew using aeroponic technology on the Mir space station in zero gravity grew even better than the same plants on Earth.
With aeroponics, plants are put into special A frames or horizontal boards, in such a way that both the top of the plant, the crown, and the bottom of the plant, the roots, are suspended in the air. In this way the crown can grow upward and the roots downward without needing any soil at all. The growers feed the plants by spraying them on a regular basis with a fine mist of a nutrient-rich, water-mix solution. As the whole system is enclosed, you save water because the nutrient mix is fully recycled within the aeroponics systems design.
Because this system allows very high-density planting and makes harvesting much easier, growers find that they have very high yields. In one study in Sardinia, Italy, researchers found that tomato plants grown aeroponically even produced four crops a year instead of the more common one or two.
In addition, because aeroponics is so appropriate for small indoor spaces, one group of growers in particular -- those that grow marijuana -- has found it especially useful for their specialist crop. Other gardeners involved in the urban gardens movement also find that aeroponics is a great way to grow fruits, vegetables and herbs in their apartments.