PHiZZ stands for pentagon-hexagon zig-zag unit and was created by Thomas Hull. You can check out his work here. Thomas Hull explains how to fold the model and assemble the balls but there is a lot of information there so I decided to make an Instructable that might be a different way to learn this awesome system.
The PHiZZ unit has quickly become one of my favorite modular origami units because of the simplicity and potential to make many different size balls. There's also a lot of math/geometry stuff that you can get into by studying these that Thomas Hull explains on his site.
I plan on making Instructables for all the PHiZZ balls that I've made so far up to a 360 unit one. I also plan on adding some videos and other fun stuff too so be sure to keep an eye out for those.
Step 1: Materials
To make a PHIZZ ball you will need 30 pieces of square paper.
Step 2: Folding the Unit
1. Start with the paper colored side up and fold in half.
2. Fold one layer to meet the middle crease so that the colored sides now show again.
3. Flip the unit over.
4. Fold the layer to meet the middle crease.
5. Fold the left corner down to meet the bottom.
6. Fold the strip to the right down to line up with the edge of the corner that was just folded.
7. Fold the strip up, using the bottom as a guide for creasing.
8. Fold the strip down, on a diagonal, lining up with the bottom.
9. Flip the unit over.
10. Fold the left corner down to line up with the bottom and last fold made.
11. The unit is now done, open it up by unfolding the zig-zags so that the paper is in a strip 1/4 the size of the original size.
Now make 29 more.
Step 3: Assembly & Preview
Once you have 30 units it's time to assemble them into a ball.
Start by insetting Piece 2 into Piece 1, as in the second picture. You'll notice that the crease lines will match up to lock it in a little.
Open the pocket on Piece 2 so that Piece 3 can be tucked into it, fifth picture.
Once Piece 3 has been tucked into Piece 2, the pocket on Piece 3 will need to be opened so Piece 1 and be tucked inside, as shown in the seventh picture.
The three pieces together will form a triangular peak. Keep adding more units in this fashion to create more triangular peaks. Eventually a ring will start to form, this is a good thing. Keep forming the ring until you have a pentagon shape as shown. To make the ball you just need to keep adding onto this ring to make more pentagon rings and eventually a ball will form.
If you get confused feel free to comment and I'll try to explain it. I'm sure once I add the how-to video it will be more clear.
Below is a video of a larger PHiZZ ball that I made and will cover soon in another Instructable.