Every atom in your body is billions of years old. Hydrogen, the most common element in the universe and a major feature of your body, was produced in the big bang 13.7 billion years ago. Heavier atoms such as carbon and oxygen were forged in stars between 7 billion and 12 billion years ago, and blasted across space when the stars exploded. Some of these explosions were so powerful that they also produced the elements heavier than iron, which stars can't construct. This means that the components of your body are truly ancient: you are stardust.
(CSSC 2005 and Photo credit from HubbleSite 2013)