Fruit set and growth in the absence of fertilization (parthenocarpy) is a useful trait in plants grown for the value of their fruit. Auxins and gibberellins are widely used to spray flowers to chemically confer parthenocarpy. In recent years, genetic modifications of either auxin or gibberellin biology have been used to confer parthenocarpy to tomato and other crops. Present knowledge indicates that parthenocarpy can be achieved by genetic modification of either auxin synthesis (iaaM), auxin sensitivity (rolB), auxin content (Aucsia) or auxin signal transduction (IAA9 or ARF8). Genetic modification of gibberellin signal transduction (DELLA) has also been shown to confer parthenocarpy. Available data, obtained under both open field and protected cultivation, show that genetic parthenocarpy can be used to improve fruit production and/or fruit quality. The mechanisms, genetically modified to confer parthenocarpy, are active also in other plant organs. Observations consistent with the Euanthial theory that envisages the fruit as a modified leaf predict that the mechanisms underlying fruit initiation have been recruited from molecular machineries present and controlling other plant developmental processes. The flower/fruit represents the last evolutionary innovation of the green plant lineage, and yet genes (i.e. Aucsia) controlling fruit initiation are most likely older than 1 billion years being present in Prasinophytes (i.e. probable ancestors of Charophytes, which themselves are considered ancestors of all land plants).