The iris is a circular, pigmented tissue that separates the anterior chamber of the eye from the posterior chamber. It has a crucial role on controlling the amount of the light entering the eye through its central opening  the pupil .<div> </div><div>The Iris has multiple important functions that support and provide image clarity on the retina. However, it is a largely neglected part of the eye, compared to the cornea lens, retina, and optic nerve, and has not been focused on in a comprehensive way until now. </div><div> </div><div>The Iris: Understanding the Essentials, combines different aspects of scientific information from a variety of fields, such as anatomy, histopathology, molecular biology, electron microscopy and other diagnostic modalities.