This is, hands down, my students FAVORITE project in Photoshop 1. Using a close up of their eye, they must select and copy on to a new layer, the iris. On another new layer, positioned on top of the iris, students put a picture. (this can be self reflective...sometimes I have them put a picture of themselves). Holding down the 'option' (on mac) they hover between the layers and click to blend the layers. (putting the pic into the iris as a mask) They then can enhance the image by using the blending modes (overlay usually looks best). I have them do 12... and they beg to do more!