LB agar is LB broth that contains agar and is typically prepared in petri dishes. The flat, solid properties of LB agar allow the plating of bacterial cultures and generation of colonies. This is widely applied in molecular cloning which relies on added antibiotics to select recombinant clones based on their acquired selection markers. In the absence of antibiotics, LB agar is nutritionally rich, allowing the growth of most microorganisms. To prepare, agar is typically added to liquid LB, then autoclaved to produce a hot, liquid solution. The media will begin to solidify around 50 degrees Celsius. Several ready-to-use mixes are available for convenience.