Start with seeds and watch them grow; then, when plants get too tall for your original kit, just snap on the 2' extension bars* and continue growing. When germinating seeds, the fixture can be kept just inches away from the seeds (or humidity dome). After sprouting, keep the fixture 3-6" away from the plant canopy. The built-in timer allows you to easily set a 12 hours on/12 hours off schedule or an 18 hours on/6 hours off schedule with a single button press.