One interesting theory on the cause of manic depression or bipolar disorder is that there is a super-fast biological clock located in the hypothalamus, in the center of the brain, which is actually a tiny cluster of nerves called the supra chiasmatic nucleus or SCN.
Since the release of the first novel, Harry Potter and the Philosopher's Stone, on 26 June 1997, the books have found immense popularity, critical acclaim and commercial success worldwide.
In December 2005, Rowling stated on her web site, 2006 will be the year when I write the final book in the Harry Potter series.. Updates then followed in her online diary chronicling the progress of Harry Potter and the Deathly Hallows, with the release date of 21 July 2007.