"Reticula and Fragments" is the theme of this new challenge. Rick and Maria introduced these two terms in their new book Zentangle Primer Volume 1.
Laura in her blog explains it like that :
"Reticula is the term for a grid, but not just the square grid like the checkerboard, but an encompassing term for all the zentangle grids. ... So with Reticula being the term for grids, fragments, then, are the pattern drawn inside each square or facet of the grid. "
I have not yet read this book but it made me want to buy it. I'm waiting for it.