Similar to the well-known human gut-resident microbes, the inside of a plant can also shelter microorganisms. Residing inside roots, stems, leaves, fruits, and even seeds, and developing a synergistic relationship with their host, these "endophytic" microorganisms need not necessarily harm the plant. Instead, they are often beneficial in germination, growth, and defense. However, plant interiors also contain many "secondary metabolites," which are natural bioactive compounds that have strong antimicrobial properties, making this environment typically hostile for microorganisms.