A very nice feature in Illustrator CC is the ability to create patterns. Basically you can create a collection of shapes, select them and then bring up the Pattern Options panel.
Go to the top right-hand corner of the panel and click on the little drop-down menu. Choose Make Pattern.
A dialog appears saying that the pattern has been added to the swatches panel. Now you have all the Pattern options available to easily change your pattern. You can change your pattern be either moving, scaling, rotating, editing the initial shape on the artboard, and/or you can just change the options within the Pattern Options panel.
For example you can use a Tile Type of Brick by Row, Brick by Column,
You can also set it to Hex by Column and Hex by Row
You can change the Width and Height…
When you are done, have a look at the top of your document and you will some buttons.
Click on Done. The Pattern options panel goes away. You can now delete your shape(s) on the artboard and check that the new pattern has appeared within the Swatches panel. Try it out - draw a new shape and apply the new pattern.
However, you can still edit the pattern, just double-click on the new pattern within the Swatches panel and the Pattern Options panel comes back again.
Now lets have a look at what we can create.
Try a simple cross (grid)…
Brick by Row, 1/3 offset…
Try the cross again but rotated 45º…
Now try hex by Column
A simple square with a line running vertically through the centre, and set to Hex by Column
Try with some circles…
In short, you can make loads of patterns very easily. Try it and see!