In this seventh entry in the New York Times–bestselling series, two unlikely best friends get creative as they prepare for the Science Fair. It's the Science Fair, and the second grade is all over it! Some kids are making man-eating robots. Some kids are holding their breath for a very, very long time. Some kids are doing interesting things with vacuum cleaners. The theme, obviously, is global warming. But what should Ivy and Bean do? Something involving explosions? Or ropes? Something with ice cubes? Or maybe . . . maybe something different. Praise for What's the Big Idea? "This seventh episode about unlikely best friends Ivy and Bean may be the most ambitious and triumphant yet . . . . Barrows and Blackall know just how to expose situations that are familiar to second-graders—with empathy and a light touch." —Shelf-Awareness