Problems with achieving it included the requirement that the deBroglie wavelength of the molecules becomes larger than their mean spacing.  
It is the basis of the Hanbury-Brown-Twiss effect and the Gross-Pitaevskii equation demonstrates why it also works for atoms having a negative scattering length.  Problems with achieving it included the requirement that the deBroglie wavelength of the molecules becomes larger than their mean spacing.  Based on the "grouping" tendencies of bosons and used to achieve an atomic laser, it was created by cooling a gas of rubidium-87 atoms to below 170 nano-kelvin by Carl Wieman and Eric Cornell.  FTP, name this form of matter predicted by Satyendra and Albert in 1925.
It is the basis of the Hanbury-Brown-Twiss effect and the Gross-Pitaevskii equation demonstrates why it also works for atoms having a negative scattering length.  
BEC or Bose-Einstein Condensate or Bose-Einstein Condensation