A process for preparing macromolecules comprising: providing: a growing macromolecule comprising a dendrimer having at least one lysine dendritic motif with an outer layer bearing functional groups and having two or more different protecting groups; a precursor for a first terminal group which is a residue of a pharmaceutically active agent; and a precursor for a second terminal group which comprises one or more of the following: PEG, polyethyloxazoli ne, or a targeting moiety selected from one or more of lectins, antibodies, functional fragments of antibodies, and ligands for cell surface receptors; deprotecting a functional group on the outer layer by removing a first protecting group; activating one of the first or second terminal group precursors; reacting the deprotected functional group with the activated terminal group precursor; deprotecting a functional group on the outer layer by removing a second protecting group; activating the other of the first or second terminal group precursors; and reacting the deprotected functional group with the activated terminal group precursor; optionally wherein a linker moiety is incorporated to mediate the attachment of the first and/or second terminal group precursors to the dendrimer; wherein the fractional abundance of a macromolecule having a particular stoichiometry is enriched compared with the fractional abundance of the macromolecule in randomly surface-functionalised macromolecules, thereby providing controlled terminal group stoichiometry; and wherein terminal group stoichiometry refers to the number and type of terminal groups. providing: a growing macromolecule comprising a dendrimer having at least one lysine dendritic motif with an outer layer bearing functional groups and having two or more different protecting groups; a precursor for a first terminal group which is a residue of a pharmaceutically active agent; and a precursor for a second terminal group which comprises one or more of the following: PEG, polyethyloxazoli ne, or a targeting moiety selected from one or more of lectins, antibodies, functional fragments of antibodies, and ligands for cell surface receptors; deprotecting a functional group on the outer layer by removing a first protecting group; activating one of the first or second terminal group precursors; reacting the deprotected functional group with the activated terminal group precursor; deprotecting a functional group on the outer layer by removing a second protecting group; activating the other of the first or second terminal group precursors; and reacting the deprotected functional group with the activated terminal group precursor; optionally wherein a linker moiety is incorporated to mediate the attachment of the first and/or second terminal group precursors to the dendrimer; a growing macromolecule comprising a dendrimer having at least one lysine dendritic motif with an outer layer bearing functional groups and having two or more different protecting groups; a precursor for a first terminal group which is a residue of a pharmaceutically active agent; and a precursor for a second terminal group which comprises one or more of the following: PEG, polyethyloxazoli ne, or a targeting moiety selected from one or more of lectins, antibodies, functional fragments of antibodies, and ligands for cell surface receptors; deprotecting a functional group on the outer layer by removing a first protecting group; activating one of the first or second terminal group precursors; reacting the deprotected functional group with the activated terminal group precursor; deprotecting a functional group on the outer layer by removing a second protecting group; activating the other of the first or second terminal group precursors; and reacting the deprotected functional group with the activated terminal group precursor; optionally wherein a linker moiety is incorporated to mediate the attachment of the first and/or second terminal group precursors to the dendrimer; wherein the fractional abundance of a macromolecule having a particular stoichiometry is enriched compared with the fractional abundance of the macromolecule in randomly surface-functionalised macromolecules, thereby providing controlled terminal group stoichiometry; and wherein terminal group stoichiometry refers to the number and type of terminal groups.