The Back Stitch is one of the more basic stitches. It makes a beautiful thin line, good for representing stems and outlines.
Back to Flat Stitches
Insert the needle in the same hole as the end of the previous stitch.
If you're stitching on fine fabric, be careful not to pull the stitch too tight, or you will create holes in the fabric. Of course, that may be what you want to do!