Star formation rate plotted against stellar mass for galaxies in different environments. Top-left: Galaxies that are members of the over-densities identified in CDFS excluding the two that host passive galaxies. Top-centre: members of the proto-cluster at z = 3.55. Upper right: members of the proto-cluster at z = 3.43. Bottom-left: field galaxies associated with the proto-cluster at z = 3.55. Bottom-right: Field galaxies associated with the proto-cluster at z = 3.43. The galaxy categories represented by the different symbols are the same as in Fig. 3.