One of the most renowned pheromone specialists, Edward O. Wilson of Harvard University, believes that “pheromones are directly related to hormones.” The latter emerged long after pheromones as their analogue for chemical communication between cells in a multicellular organism. Aggregation pheromones are probably the oldest. Even in times when there were no multicellular organisms on Earth, they helped facilitate communication between cells of the same species. Thanks to them, bacterial conjugation is also possible. Aggregation pheromones also underlie the formation of unicellular colonies, some of which are so stable that they are also referred to as multicellular organisms. These include, for example, the flagellates of the genus Volvox (Fig. 1).