The aim of this article is to highlight some previous challenges that were also a stimulus to finding proof for some interesting results. With this pretext, we present three moments in the history of mathematics that were important for the development of new lines of research.

The Russian mathematician Grigori Perelman did not accept the Fields Medal in 2006 and refused the million dollar prize for solving Poincaré's conjecture, one of the millennium problems, in 2010.

The Clay Mathematics Institute made a list of seven problems in May 2000; they were called the «millennium problems». Finding their solution has an added incentive: each solver will receive a million dollars as a prize.