context: 1. e2e4  1... c7c5  2. g1f3  2... b8c6  3. d2d4  3... c5d4  4. f3d4  4... g8f6  5. b1c3  5... e7e5  6. d4b5  6... d7d6  7. c3d5 Since it was used in some games of the Carlsen-Caruana match, this move has become as important to opening theory as the old main line with 7.Bg5. 7... f6d5  8. e4d5 This is considered better than the alternative 8...Ne7.