Hydroponics is a subset of hydroculture and is a method of growing plants using mineral nutrient solutions, in water, without soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite, gravel, mineral wool, expanded clay or coconut husk.​
Researchers discovered in the 18th century that plants absorb essential mineral nutrients as inorganic ions in water.[citation needed] 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.

​Hydroponic nutrient solutions are often custom formulated to suit the crop being grown. The delivery method is nearly as variable. For the home hobbyist, the most common type is static solution culture--allowing the solution to surround the plant roots and being refreshed manually on a periodic basis. Next in popularity is continuous flow in which a constant stream of nutrient solution is pumped through the growing medium.