In the mid-90′s when I was working on my Tessellation Tutorial pages (which, by the way, helped me land my Math Forum job!) I had an online conversation with Michael South. I still have never met Michael in person but I remember feeling honored that he would take the time to contact me and engage in a conversation about whether some of what I was presenting as being a tessellation really was or was not. I captured part of our conversation on this webpage:
The ideas Michael and I discussed have stayed in the back of my mind and surface whenever I see something that is a repeating pattern. I often wonder what the unit is. Is the frog wallpaper in the ladies’ restroom in the Osteria Marco restaurant in Denver, CO a tessellation? Is it really made up of squares and the frogs are the decoration within each square? Or does it, at least, give that illusion? Whether it’s a tessellation (in the stricter mathematical sense) or not, it definitely caught my eye — the color, the fun frogs and the pattern. Annie had to go look for herself and she took the photo above after I showed her my photos and requested one of the “unit”!