A method for determining the concentration of at least one protein in a sample comprising the steps: (a) providing: (i) at least one protein; (ii) a first protein probe specific for a first region of said at least one protein, wherein said first protein probe is attached to a first capture region or a first matrix; (iii) a second protein probe specific for a second region of said at least one protein, wherein said second protein probe comprises a signal oligo; and (iv) when said first probe is attached to a first capture region: a second matrix having attached thereto a moiety which is capable of binding to said capture region in said first protein probe; (b) forming at least a first complex comprising said at least one protein, said first protein probe, and said second protein probe, wherein said at least one protein is bound to said first and second protein probes, and wherein when said first probe is attached to a first capture region said capture probe is bound to said moiety in said second matrix; (c) releasing said signal oligo from said first complex; (d) forming a second complex comprising at least said signal oligo and at least one oligo probe comprising a signal oligo-specific region and a region comprising a nanoreporter wherein said nanoreporter comprises a plurality of different detectable labels; (e) individually detecting said second complex or at least part of said second complex by a method comprising individually counting the presence of the plurality of different detectable labels of said nanoreporter, wherein the count of the plurality of different detectable labels is indicative of the concentration of said protein in said sample. (a) providing: (i) at least one protein; (ii) a first protein probe specific for a first region of said at least one protein, wherein said first protein probe is attached to a first capture region or a first matrix; (iii) a second protein probe specific for a second region of said at least one protein, wherein said second protein probe comprises a signal oligo; and (iv) when said first probe is attached to a first capture region: a second matrix having attached thereto a moiety which is capable of binding to said capture region in said first protein probe; (i) at least one protein; (ii) a first protein probe specific for a first region of said at least one protein, wherein said first protein probe is attached to a first capture region or a first matrix; (iii) a second protein probe specific for a second region of said at least one protein, wherein said second protein probe comprises a signal oligo; and (iv) when said first probe is attached to a first capture region: a second matrix having attached thereto a moiety which is capable of binding to said capture region in said first protein probe; (b) forming at least a first complex comprising said at least one protein, said first protein probe, and said second protein probe, wherein said at least one protein is bound to said first and second protein probes, and wherein when said first probe is attached to a first capture region said capture probe is bound to said moiety in said second matrix; (c) releasing said signal oligo from said first complex; (d) forming a second complex comprising at least said signal oligo and at least one oligo probe comprising a signal oligo-specific region and a region comprising a nanoreporter wherein said nanoreporter comprises a plurality of different detectable labels; (e) individually detecting said second complex or at least part of said second complex by a method comprising individually counting the presence of the plurality of different detectable labels of said nanoreporter, wherein the count of the plurality of different detectable labels is indicative of the concentration of said protein in said sample.