A method of making a multispecific antibody comprising at least two first antigen binding regions and at least two second antigen binding regions, said first and second antigen binding regions having a common light chain, wherein the first antigen binding regions have a different antigen specificity than the second antigen binding regions, the method comprising the steps of: i) isolating a first antigen binding region having specificity for a first antigen comprising at least one light chain and a heavy chain, and further isolating the at least one light chain thereof; ii) isolating heavy chains having specificity for a second antigen from the output of a selection performed from a naive library against the second antigen; iii) preparing a restricted library comprising the heavy chains having specificity for the second antigen isolated in step ii) and the at least one light chain having specificity for the first antigen isolated in step i); iv) performing a selection against the second antigen from the restricted library prepared in step iii); v) isolating a second antigen binding region having specificity for the second antigen from the selection performed in step iv), wherein the second antigen binding region comprises the at least one light chain against the first antigen isolated in step i); and vi) incorporating the first antigen binding region isolated in step i) and the second antigen binding region isolated in step v) into a multispecific antibody; wherein the multispecific antibody comprises an IgG moiety comprising either: a) the first antigen binding region of the multispecific antibody; or b) the second antigen binding region of the multispecific antibody; and two Fab moieties, wherein each Fab moiety comprises either: a) the second antigen binding region of the multispecific antibody; or b) the first antigen binding region of the multispecific antibody; wherein the N-terminus of the heavy chain of one Fab moiety is linked to the C-terminus of the Fc region of one heavy chain of the IgG moiety via a linker moiety, and the N-terminus of the heavy chain of the other Fab moiety is linked to the C-terminus of the Fc region of the other heavy chain of the IgG moiety via a linker moiety. i) isolating a first antigen binding region having specificity for a first antigen comprising at least one light chain and a heavy chain, and further isolating the at least one light chain thereof; ii) isolating heavy chains having specificity for a second antigen from the output of a selection performed from a naive library against the second antigen; iii) preparing a restricted library comprising the heavy chains having specificity for the second antigen isolated in step ii) and the at least one light chain having specificity for the first antigen isolated in step i); iv) performing a selection against the second antigen from the restricted library prepared in step iii); v) isolating a second antigen binding region having specificity for the second antigen from the selection performed in step iv), wherein the second antigen binding region comprises the at least one light chain against the first antigen isolated in step i); and vi) incorporating the first antigen binding region isolated in step i) and the second antigen binding region isolated in step v) into a multispecific antibody; wherein the multispecific antibody comprises an IgG moiety comprising either: a) the first antigen binding region of the multispecific antibody; or b) the second antigen binding region of the multispecific antibody; and two Fab moieties, wherein each Fab moiety comprises either: a) the second antigen binding region of the multispecific antibody; or b) the first antigen binding region of the multispecific antibody; wherein the N-terminus of the heavy chain of one Fab moiety is linked to the C-terminus of the Fc region of one heavy chain of the IgG moiety via a linker moiety, and the N-terminus of the heavy chain of the other Fab moiety is linked to the C-terminus of the Fc region of the other heavy chain of the IgG moiety via a linker moiety. an IgG moiety comprising either: a) the first antigen binding region of the multispecific antibody; or b) the second antigen binding region of the multispecific antibody; and a) the first antigen binding region of the multispecific antibody; or b) the second antigen binding region of the multispecific antibody; and two Fab moieties, wherein each Fab moiety comprises either: a) the second antigen binding region of the multispecific antibody; or b) the first antigen binding region of the multispecific antibody; a) the second antigen binding region of the multispecific antibody; or b) the first antigen binding region of the multispecific antibody; wherein the N-terminus of the heavy chain of one Fab moiety is linked to the C-terminus of the Fc region of one heavy chain of the IgG moiety via a linker moiety, and the N-terminus of the heavy chain of the other Fab moiety is linked to the C-terminus of the Fc region of the other heavy chain of the IgG moiety via a linker moiety.