Hydroponics is growing a plant without soil usually in an inert substance such as rockwool, perlite, or a soilless media to hold the roots for water and nutrient absorption. Hydroponics dates back several hundreds of years as there is evidence that ancient civilizations grew plants in water.
Nutrients are vital to the success of growing. There are 16 essential elements that a plant needs to grow and the right balance of these nutrients must be maintained for each specific variety of plants. Equally as important as nutrition are the factors of light, temperature (heating & cooling), CO2 and overall environmental control. Insects play a key role in pollination and pest management. When you combine all of these factors, you have a controlled environment which is a hydroponic greenhouse.