A method for reversible staining of cells comprising the steps: (a) providing a sample comprising a cell having a receptor molecule on the surface of the cell, (b) contacting said cell with (i) at least one receptor ligand capable of binding to said receptor molecule wherein said at least one receptor ligand is conjugated to at least one first partner of a binding pair consisting of at least one first partner and at least one second partner, wherein the receptor ligand and the receptor molecule exhibit a low-affinity interaction; the dissociation constant K d of which is in the range of 10 -2 to 10 -7 M; (ii) at least one second partner of said binding pair that has at least two binding sites for said first partner; and (iii) a detectable label bound to or capable of binding to the at least one receptor ligand (i) and/or the at least one second partner (ii); wherein the first partner and the second partner of the binding pair are capable of forming a reversible bond, wherein the reversible bond has a K d between 10 -5 and 10 -13 M, and wherein an aggregate comprising at least two receptor ligands (i), at least one second partner (ii) and at least one detectable label (iii) is bound via the receptor molecule to said cell, thereby reversibly staining said cell, (c) optionally separating said stained cell from other components of said sample and (d) optionally removing said staining from said cell by disrupting the reversible bond between the first partner and the second partner. (a) providing a sample comprising a cell having a receptor molecule on the surface of the cell, (b) contacting said cell with (i) at least one receptor ligand capable of binding to said receptor molecule wherein said at least one receptor ligand is conjugated to at least one first partner of a binding pair consisting of at least one first partner and at least one second partner, wherein the receptor ligand and the receptor molecule exhibit a low-affinity interaction; the dissociation constant K d of which is in the range of 10 -2 to 10 -7 M; (ii) at least one second partner of said binding pair that has at least two binding sites for said first partner; and (iii) a detectable label bound to or capable of binding to the at least one receptor ligand (i) and/or the at least one second partner (ii); wherein the first partner and the second partner of the binding pair are capable of forming a reversible bond, wherein the reversible bond has a K d between 10 -5 and 10 -13 M, and wherein an aggregate comprising at least two receptor ligands (i), at least one second partner (ii) and at least one detectable label (iii) is bound via the receptor molecule to said cell, thereby reversibly staining said cell, (i) at least one receptor ligand capable of binding to said receptor molecule wherein said at least one receptor ligand is conjugated to at least one first partner of a binding pair consisting of at least one first partner and at least one second partner, wherein the receptor ligand and the receptor molecule exhibit a low-affinity interaction; the dissociation constant K d of which is in the range of 10 -2 to 10 -7 M; (ii) at least one second partner of said binding pair that has at least two binding sites for said first partner; and (iii) a detectable label bound to or capable of binding to the at least one receptor ligand (i) and/or the at least one second partner (ii); (c) optionally separating said stained cell from other components of said sample and (d) optionally removing said staining from said cell by disrupting the reversible bond between the first partner and the second partner. <EOS>