Color-enhanced Scanning Electron Micrograph (SEM) of an expanded clay aggregate pebble used in hydroponic (soilless) gardening. This is a lightweight ceramic manufactured in a rotating kiln. This material has a very high surface area due to all the holes and cracks. It is able to collect hydroponic chemicals and air to nurture the roots of a plant, making it an excellent delivery method for nutrients. Plants can grow at maximum rates using expanded clay aggregate. A typical hydroponic system will wet the aggregate several times a day. Magnification: 33X when printed at 10 cm wide.