11.   Historically, doctors have treated this problem, called stenosis, with balloon angioplasty, in which a tiny balloon is inflated to push apart vessel walls.

12.   In angioplasty, doctors snake a catheter to the heart through a vein in the leg, then inflate a balloon on the end to clear blockage.

13.   Inflating the balloon locks the stent in place and forms a rigid support to hold the artery open.

14.   Message originators inflated balloons, wrote messages on them, then lofted the balloons in the general direction of the recipients.

15.   Once threaded to the main artery supplying the heart, the balloon is gently inflated with a saline solution.

16.   Once in place, the balloon is inflated, pressing the arterial plaque against the artery walls.

17.   Once the catheter reaches the desired artery, surgeons inflate the balloon.

18.   The balloon is then inflated to compress artery-clogging plaques against the arterial walls, which widens the opening and increases blood flow.

19.   The balloon is then inflated, stretching the ligament and making more room for the nerve.

20.   The balloons were inflated less to reduce their buoyancy, and flown lower and at an angle to make them harder for the wind to catch.