The aerial surfaces of many plant species are lined in hairs (trichomes). The morphology of those buildings can differ enormously among species, and also to easy hairs, extra complicated multicellular constructions usually take place. The latter are usually inquisitive about secretion of phytochemicals, a lot of which (e.g., the basic oils utilized in flavourings and fragrances) are widespread. Their application as version platforms to appreciate cell-to-cell circulate and telephone differentiation, in addition to their power software in biotechnology, has generated renewed curiosity in those constructions. during this quantity, plant scientists from assorted backgrounds current experiences which summarise our present figuring out of those constructions. Their ultrastructure, biochemistry, differentiation and improvement, in addition to their physiological and ecological roles, are mentioned. the amount will hence be of curiosity to researchers from numerous fields.