Identical twins share the same key outer features, for example hair and eye color.  Because identical twins have the same genetic make-up, they have the same blood groups, Rhesus factor and all genetically-related features. Non-identical twins do not have the same genetic make-up, but do grow at the same time in the womb. In this film we will find out more about the difference between identical and non-identical twins and about the important question of environmental influences and disposition in the forming of characteristics in twins.