The term 'heterosis' (or hybrid vigour) characterizes the increased ability or a hybrid as compared to the parental forms. The term ability means the favourable changes in hybrid characters when compared to the abilities of P (Parental) in one or several characters. The term heterosis was first coined by Shull in 1914. Generally heterosis manifested as an increase in vigour, size, growth, yield or some other characteristics. But in some cases, hybrid may be inferior to the weaker parent this is also regarded as heterosis. This phenomenon was discovered in the 18th century by Veldeiter during experiments on tobacco hybridization and later confirmed by many selectionists working on hybridization of plants and animals. The information found herein should give breeders, geneticists, and biologists additional insights into the complexity of heterosis. It is clear from the symposium contents that old questions regarding heterosis and its relative importance resurfaced, and new questions were defined in the light of emerging technologies.