SAVE $50: Both the 10-ounce and 14-ounce Ember Smart Mugs are on sale at Best Buy for $79.99 and $99.99, respectively. That's up to 39% in savings. But act fast, as the 10-ounce option is part of ...

Phase-change materials change from one state to another (such as from a solid to a liquid) when exposed to heat, absorbing some of that heat and storing it as energy in the process. As they cool ...