Just Rhombii by Joel Cooper/Peter Keller
I did mine with a 32 division grid.
Peter Keller did a photo tutorial on how to fold it on his flickr account.
There's an extra flourish at the center that I've not attempted. I just wanted the field of rhombuses.
His tutorial is a photo series of how he folded the design. It was quite helpful in understanding the structure. But personally, I prefer a crease pattern for understanding how to fold tessellations. That's just how my mind figures these things. So I mapped one out before beginning my attempt.
All the rhombuses are mountain folds. All the hexes and triangles are valley.
I folded my version very differently from the tutorial. When I fold flagstones I approach them in a very simple way. I do all the preceasing to set things up. Then I just work my way outwardly from the center easing all the folds into place.
I first set the initial hexagon twist and the inner most set of rhombuses. After that, it's just a gradual conditioning of the paper. Working outward in a circular fashion. Slowly coaxing all the iterations into their proper places. When they're all relatively set, they go under some heavy books to flatten overnight.
First photo is a backlit rendition. Second is the solid.
Last photo is the crease pattern. It's a relatively small version, but it's still quite plain to see how the design repeats ad infinitum whatever size grid you choose.