An agar plate is a laboratory tool used to grow and study microorganisms, such as bacteria and fungi. It consists of a petri dish filled with a gelatinous substance called agar, which is derived from seaweed. This medium provides nutrients that support the growth of various organisms, allowing scientists to observe their characteristics and behaviors. Researchers often use agar plates to isolate specific strains of microorganisms or to test the effectiveness of antibiotics. By spreading a sample on the agar surface, they can see how different organisms interact and grow, making it a vital tool in microbiology and related fields.