They have been called spectacles to help you see right into heaven and they have caused one of the greatest theological debates, lasting over a century. They have caused grown men to convert to Christianity and others to fling them furiously into the flames. Men and women have died for the right for them to be venerated. So what is it about icons that causes these extremes of behaviour? What are they and how are they made. What can we learn from them about how our ancestors worshipped and do they have mirrors in western Christianity? Find out more about these exceptionally beautiful images, crafted through spirituality