1 INTRODUCTION  
2 DESCRIPTION OF THE PROBLEM  
2.1 The phase-space mapping problem  
2.2 Previous velocity and displacement field reconstructions  
3 THE COSMIC BIRTH APPROACH  
3.1 The Gibbs-sampling scheme  
3.2 Step 1: sampling the linear density field  
3.3 Steps 2 & 3: displacements and peculiar velocity fields  
3.4 Step 4: response function in Lagrangian space  
3.5 Step 5: Sampling the galaxy-dark matter bias relation  
4 VERIFICATION OF THE COSMIC BIRTH CODE  
4.1 Data used in this work  
4.2 Results  
5 DISCUSSION AND CONCLUSIONS