How is it possible that indentical twins have the same genetic material but are two different individuals?

Gnomon

We are all a combination of what we inherit from our parents and what we experience. Identical twins inherit exactly the same information from their parents but have different lives from long before they are born, which influence the characters of the twins. Even so, identical twins tend to be far more similar in character than any other pair of people. Jul 17 06, 6:30 AM

zbeckabee

"At first glance identical twins seem, well, identical. In fact many of these sibling pairs show minor physical variations and differences in characteristics such as susceptibility to disease. Just what causes these dissimilarities is unclear. But a new report further suggests that epigenetic factors--that is, differences in how the genome is expressed--could be responsible." http://www.sciam.com/article.cfm?articleID=0001616A-93A1-12C5-93A183414B7F0000 Jul 17 06, 8:46 AM