You may have never heard of Catherine Hettinger, but she's the woman behind the fidget spinner--the gadget that is quickly turning into the must-have toy of 2017.

The toy has gained the popularity of kids and adults across the globe, and its different versions make up 19 of Amazon's top 20 best-selling products. Yet Hettinger, who held the patent for the device until 2005 but let it lapse because she couldn't afford the $400 fee, hasn't seen a penny of profit, according to The Guardian.

"Several people have asked me: 'Aren't you really mad?'" Hettinger told the newspaper in a recent interview. "But for me I'm just pleased that something I designed is something that people understand and really works for them."

The gadget consists of a ball bearing in the middle of a three-pronged metal or plastic device, which allows it to be flicked or spun around. Hettinger, who now lives in Florida, told Time that she first thought of the idea while witnessing kids throwing rocks at police officers in Israel, and started thinking about how to provide a more peaceful outlet for them. Her mind, she explains, starts looking for solutions whenever it sees a problem.

Hettinger, a New York's Rensselaer Polytechnic Institute alumna, has said that she's planning to launch a Kickstarter campaign, the "Classic Spinner" to sell her version online.