Poincaré conjecture

The Poincaré conjecture, proposed by French mathematician Henri Poincaré in 1904, is a fundamental problem in topology, which studies the properties of space. It asserts that every closed, three-dimensional shape without holes is essentially a sphere. In simpler terms, if you can stretch and deform a shape without tearing or gluing, any shape resembling a three-dimensional sphere can be transformed into a true sphere. The conjecture remained unproven for nearly a century until it was confirmed by mathematician Grigori Perelman in 2003, marking a significant milestone in mathematics.