In 1987, Miles Reid conjectured that a combination of contracting (resp. introducing) some isolated curves and smoothing (resp. singularizing) deformation connects all Calabi-Yau 3-folds to each other, as well as to a (non-Kähler, ) connected sum of copies of , called a rakshasa, thus connecting their individual moduli spaces into an irreducible object: The moduli space of 3-folds with may nevertheless be irreducible, Math. Ann. 278 no. 1-4, (1987) 329–334 (doi:10.1007/BF01458074). This implies...