Ibn Sina wrote many books on various scientific branches, many of which are on philosophy, religion, music, medicine, astronomy, physics, and natural sciences. Some sources state that the number of books he has written is over 240; 153 of these have been discovered. Among his valuable books, the two most well-known books are «al-Shifa», which deals mostly with philosophy, and the five-volume «al-Qānūn Fī al-Tibb», which is a complete medical encyclopedia. The Little Qanun is the model of «al-Qānūn». The idea of publishing this book struck the author's mind when he thoroughly dealt with Avicenna's views and thoughts. It is hard to imagine such discoveries were generated more than one thousand years ago.