Balloons may be just a bunch of hot air, but it takes more than that to keep them afloat when they're giant size. Designers at Macy's Parade Studio craft miniature 3-D molds to carefully plan inflation and deflation ports; during construction, helium-barrier fabrics are used to keep the element securely inside--particularly important as "pinholes can deflate a chamber," says John Piper, studio VP. (He knows this too well--in 2005, a gust of wind sent the M&M balloon out of control, causing it to deflate and injure two onlookers.) As extra insurance, new radio modifications will help balloon handlers communicate. "If you're 4 or 94," says Piper, "you get excited when those balloons go into the sky." As long as they stay there.