Hydroponics (from the Greek words hydro water and pono labor) is a method of growing plants using mineral nutrient solutions, without soil.
Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as gravel, or mineral wool.
Plant physiology researchers discovered in the 19th century that plants absorb essential mineral nutrients as inorganic ions in water. In natural conditions, soil acts as a mineral nutrient reservoir but the soil itself is not essential to plant growth. When the mineral nutrients in the soil dissolve in water, plant roots are able to absorb them. When the required mineral nutrients are introduced into a plant's water supply artificially, soil is no longer required for the plant to thrive. Almost any terrestrial plant will grow with hydroponics. Hydroponics is also a standard technique in biology research and teaching.
When most people think of hydroponics, they think of plants grown with their roots suspended directly into water with no growing medium. This is just one type of hydroponic gardening, known as N.F.T. (Nutrient Film Technique). There are several variations of N.F.T. used around the world and it is a very popular method of growing hydroponically. What most people don't realize is that there are literally hundreds of methods of hydroponic gardening.