This poor hydroponics section of the forum hasn't been frequented much by the looks of it so I thought it might be beneficial to get a new post in here. This is going to be geared towards The Kratky Method of growing hydroponically. It's the most simple and thus the easiest to start if you're a beginner. If you don't know, hydroponics is a technique for growing plants in the absence of soil, and instead using water and dissolved nutrients. Professor Kratky from the University of Hawaii came up with the process and hence is where the name is derived. Nutrients are dissolved in water and held in an opaque container, which is termed the reservoir. Blocking the light is important, it minimises the chance of algal growth in the reservoir which would compete with your plants for nutrients. Holes are cut into the lid of the reservoir large enough to fit net pots (usually 3" diameter). The plants are then placed in the net pots and surrounded by an inert growing medium such as expanded clay balls, the lid placed back over the reservoir. If the roots are long enough as it is and they reach the nutrient solution, you're good to go. If they're too short still, you will have to regularly pour nutrient solution over the roots from the top until they get to the desired length. Plants need oxygen like the rest of us. As roots grow, the level of the nutrient solution lowers and exposes the root system to more air and thus oxygen. It's really this simple but other systems do increase in complexity. For more info and picture for more explanation, check out this article on The Kratky Method.