A simple question about a spinning needle has haunted mathematicians for more than a century. It led to the Kakeya conjecture, a cornerstone of modern analysis connecting geometry, fractals, and the behavior of waves. Now, mathematicians Hong Wang and Joshua Zahl have cracked the 3D case — a once-in-a-generation breakthrough that could reshape how we understand the Fourier transform. (Also featuring Terence Tao and Jonathan Hickman.)