The stems of these hearts are fibers that have been bridged between the heart balloons and the box. Because of the flexibility of the bridged fiber, the heart balloons wobble and sway when you shake the box. I have spent countless hours refining my bridging techniques, but there are many more discoveries to be made on this subject. Feel free to leave a comment if you have any questions. If you new to the process of bridging, then the Spyder Bytes: Bridging Techniques tutorial is a must. You’ll find a ton of useful tips and techniques there.