Agarwood, also known as oud or aloeswood, is a fragrant dark wood that forms in the heartwood of the Aquilaria tree when it becomes infected with a specific type of mold. This infection triggers the tree to produce a dense, aromatic resin as a defense mechanism, which is highly valued for its unique scent. The wood is primarily found in Southeast Asia and is used in various applications, including perfumes, incense, and traditional medicine. Due to its rarity and the lengthy process required for its formation, agarwood is one of the most expensive natural raw materials in the world.