ThermalTech's jackets don't look too different from a North Face, but the company promises they're more unique (and less bulky) than the standard fare. See, they sandwich a "smart" fabric layer made of lightweight stainless steel yarn in between the outer layer and the lining. That fabric absorbs UV rays from the sun and converts whatever it collects into heat to keep you warm. The company says the jackets can reach 18 degrees F in just two minutes under the sun even when it's cold. You don't have to worry even if a snowstorm's blocking out the sky either -- the jackers can absorb energy from artificial light, as well.