The world of crochet seems to be ever evolving, and one technique that I have seen recent renewed interest in is the “extended stitches”. Extended stitches are essentially the same stitches as are regularly used, single, half double, double, treble, etc. however they have an extra pull through making them slightly taller.

Begin an extended double crochet just as you would a typical double crochet; yarn over, insert hook in indicated space, yarn over, pull up a loop

This stitch type is really nice is you are created a fabric that has gradual height changes as an extended single crochet is slightly taller than a single crochet, yet slightly shorter than a half double crochet, creating a very nice gradient of height by using the three stitches together.
To create an extended stitch, you begin as you do for the standard stitch, for example for a double crochet and an extended double crochet you; yarn over, insert hook in indicated stitch, yarn over, pull through up loop. Now, this is where the only difference now takes place, for an extended stitch, you chain 1, then continue as you would with the remainder of the stitch, yarn over pull through 2, twice.

Next, Chain 1, then complete the stitch as normal, Yarn over, pull through 2, twice

By simply creating a chain stitch at the very base of the typical stitch you create this extra height. Another interesting creation with this stitch is that it creates a fabric that is a little more “stretchy” than the traditional stitch, while giving a very similar appearance. I often mix this stitches in items that I create in a free form style to allow for smoother transition of styles, and I also use then mixed with more traditional stitches to create fabrics with subtle texture changes.

See the subtle difference between the stitch on the left and the one adjacent, the bottom of the stitch as a little more height before the first bar in the post

I hope this clears up any mysteries about this simple adjustments to everyday stitches, that can easily be added to you foundation of stitch knowledge.