One of the best options for Black, along with developing the bishop on e7 or b4.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. g2g3  3... d7d5  4. f1g2 The Catalan opening is one of the most important in chess. Nowadays, every professional chess player must be familiar with its theory.