The invention is directed to a fluorescent dye according to the general formula I: with C is a core moiety comprising 20 to 200 atoms; S same or different ether residues comprising 1 to 10 carbon atoms; n is an integer ranging from 2 to 500; m is an integer ranging from 0 to 500; x is an integer ranging from 2 to 50; y is an integer ranging from 1 to 50; R same or different residue comprising a reactive group capable of forming a covalent bond with a biomolecule; F same or different fluorophores covalently bound to (S)n. The fluorescent dyes can be conjugated to a biomolecule and used for flow cytometry and/or by fluorescence microscopy.