Blichfeldt's theorem: https://en.wikipedia.org/wiki/Blichfeldt%27s_theorem

Any set in the plane of area greater than one can be translated to contain two integer points. New article on Wikipedia, connected to an expansion of the biography https://en.wikipedia.org/wiki/Hans_Frederick_Blichfeldt of Hans Blichfeldt, who came to the US from Denmark as a teenager in 1888 and worked for several years as a lumberman, railway worker, and surveyor before his mathematical talent was recognized and he became one of the first students at Stanford.