Being that my name is indeed Tess, I have a slight fascination  with "Tessellations". This in particular one was done by an artist named M.C. Escher. He's one of the artists that better known for their Tessellation's. This one was done in 1938 and is called "Day and Night". I love the way it clearly translates from day to night or light to dark. The contrast is interesting. It's also interesting how the shape of the birds translate into a completely different shape, becoming checkered like.