A branch of agriculture, hydroponics is a soil-free method used to grow many types of plants. Depending on the type of hydroponic system used, the plants' roots are suspended in, flooded with or misted with nutrient-rich water that provides them with all the nutrients they need for healthy growth. While the history of hydroponic gardening is believed to date back to at least 600 B.C., in our society this soil-less method of growing plants has really taken off only recently.