Smocking is an extremely tedious method that yields great results. It involves plotting a pattern on a grid drawn onto a piece of cloth, then hand sewing through that pattern. It creates a three-dimensional texture on what was once a two-dimensional cloth. The smaller the grid squares, the more intricate the pattern.
I created a smocked cloth with grid squares that were 2cm wide. It took almost a whole weeks idle time to finish sewing it. Mid-way through I tried it as a means for creating a poofy sleeve.
I also smocked with a machine by loading elastic thread into the bobbin.