Although it reports directly to the Pontiff, the Academy has considerable freedom in conducting its mission: the study of Science and the possible consequences for the human condition. Christian belief is not a prerequisite for membership to the Academy, because first and foremost, it is a legitimate Scientific body that follows the Scientific Method. As of 2003 more than two dozen Nobel Prize winners (including Professor Ahmed Zewail, Chemistry 1999) and several Field Medal winners were counted as members. Plenary sessions are interdisciplinary events held every other year to review new developments and discus progress made towards their mission. Common working groups include astronomy and cosmology, cognition and brain science, and genetics.