Nellie Durand, master quilter and fiber artist, writes:

"I've been sewing with machines for over 50 years and never knew how the stitches were made. This website has an animated illustration of how the upper and bobbin threads interlock (scroll half way down). Amazing! Now I know how all those little parts I'm so familiar with actually function. Yeah!"

Check out HOW A STICHING MECHANISM IN A SEWING MACHINE WORKS by MIT student Jonah Elgart