Abstract <p>Histological events occurring in morphogenic calluses of <i>Lavandula angustifolia</i> Mill. are described for the first time for a long-term (2–5 passages) in vitro culture. In the calluses of passage 2, buds and leaves of normal structure (the <i>de novo</i> organogenesis pathway) as well as somatic embryos of normal structure originating from cells of the bud epidermis (the somatic embryogenesis in vitro pathway) were revealed. As the calluses were cultivated further, their normal morphogenetic potential was gradually lost. While only the buds were characterized by the normal structure in the calluses of passage 3, and the leaves had an abnormal structure, buds of mainly abnormal structure were noted in the calluses of passage 4, and only structurally degenerated tissues were noted in the calluses of passage 5. The question about reducing the properties of pluri- and totipotency of callus cells as they were cultured in vitro is discussed. The histological data obtained can be used in choosing the duration of a callus culture in vitro to obtain full-fledged regenerants of this valuable essential oil and medicinal plant in various cell biotechnologies.</p>