A method of preparing a nucleic acid sample for sequencing, wherein the sample comprises at least 10 cells, wherein the sample of cells has been incubated with a pool of two or more different barcoded affinity probes, wherein the pool comprises a first barcoded affinity probe comprising a first affinity moiety and a first probe-barcode oligonucleotide, wherein the first affinity moiety is capable of binding to a first target protein, and a second barcoded affinity probe comprising a second affinity moiety and a second probe-barcode oligonucleotide, wherein the second affinity moiety is capable of binding to a second target protein, wherein each probe-barcode oligonucleotide comprises a barcode sequence associated with and/or identifying of the affinity moiety to which it is linked, and wherein the method comprises the steps of: (a) contacting the sample with a library comprising at least two multimeric barcoding reagents, wherein each multimeric barcoding reagent comprises first and second barcoded oligonucleotides linked together and a cell-binding moiety, wherein the barcoded oligonucleotides each comprise a barcode region and wherein the barcode regions of the first and second barcoded oligonucleotides of a first multimeric barcoding reagent of the library are different to the barcode regions of the first and second barcoded oligonucleotides of a second multimeric barcoding reagent of the library, wherein the cell-binding moiety of the first multimeric barcoding reagent binds to the cell membrane of a first cell prior to step (b), and wherein the cell-binding moiety of the second multimeric barcoding reagent binds to the cell membrane of a second cell prior to step (b); (b) lysing the cells or permeabilizing the cell membranes of the cells; and (c) annealing or ligating the first and second barcoded oligonucleotides of the first multimeric barcoding reagent to first and second sub-sequences of a target nucleic acid of the first cell to produce first and second barcoded target nucleic acid molecules, and annealing or ligating the first and second barcoded oligonucleotides from the second multimeric barcoding reagent to first and second sub-sequences of a target nucleic acid of the second cell to produce first and second barcoded target nucleic acid molecules, wherein the cells are comprised within a single contiguous aqueous volume during steps (a), (b) and (c), and wherein the target nucleic acids comprise probe-barcode oligonucleotides within the barcoded affinity probes. (a) contacting the sample with a library comprising at least two multimeric barcoding reagents, wherein each multimeric barcoding reagent comprises first and second barcoded oligonucleotides linked together and a cell-binding moiety, wherein the barcoded oligonucleotides each comprise a barcode region and wherein the barcode regions of the first and second barcoded oligonucleotides of a first multimeric barcoding reagent of the library are different to the barcode regions of the first and second barcoded oligonucleotides of a second multimeric barcoding reagent of the library, wherein the cell-binding moiety of the first multimeric barcoding reagent binds to the cell membrane of a first cell prior to step (b), and wherein the cell-binding moiety of the second multimeric barcoding reagent binds to the cell membrane of a second cell prior to step (b); (b) lysing the cells or permeabilizing the cell membranes of the cells; and (c) annealing or ligating the first and second barcoded oligonucleotides of the first multimeric barcoding reagent to first and second sub-sequences of a target nucleic acid of the first cell to produce first and second barcoded target nucleic acid molecules, and annealing or ligating the first and second barcoded oligonucleotides from the second multimeric barcoding reagent to first and second sub-sequences of a target nucleic acid of the second cell to produce first and second barcoded target nucleic acid molecules,