I once heard of this structure on the Discovery Science channel and have since forgotten the name. The details I remember about it were that it is the central time-keeping device for the brain located in the geographic center of the human brain. The DSC only mentioned it in passing to describe a person with an abnormality in this structure. Can someone post some reliable research links and a short description of it? I don't trust google much and am not good at using it, so thanks!
You are probably referring to the suprachiasmatic nucleus.
Note that, although this is the central clock, there are also so-called "peripheral clocks", for instance in the liver, pituitary and other organs that can finely tune rhythms in the organism.
You may also want to have a look at the Wikipedia page for circadian clock and references therein.