The crinkled edges of a lettuce leaf curve and expand in a shape that has perplexed mathematicians for centuries. Those curves - an example of a high-level geometry concept called the hyperbolic plane - were not even defined by geometry theorists until the 19th century. And in the almost 200 years following, mathematicians struggled to find a way to model the complex shape known as the geometric opposite of the sphere. Then mathematician Daina Taimina picked up her crochet needles and some synthetic yarn, and the problem was solved. In 1997, Taimina, of Cornell University, found a way to crochet her way into "hyperbolic space." Her woolen creations, which resemble crenulated flowers and hair scrunchies, became the first physical models of the hyperbolic plane. [read more on NPR.org]