An in vitro method of detecting an analyte in situ in a sample, said method comprising: (i) contacting said sample with at least a pair of proximity probes each comprising a proteinaceous target-binding domain coupled to a nucleic acid domain and allowing the proximity probes to bind, in proximity, to their respective target, said target being either the analyte or a binding partner for the analyte; (ii) further contacting said sample with a set of at least two padlock probes, wherein each padlock probe comprises two oligonucleotides, each oligonucleotide being capable of binding to the nucleic acid domains of at least the said pair of proximity probes such that the respective ends of the oligonucleotides of each padlock probe are brought into juxtaposition for ligation when said proximity probes have bound to their target in proximity, a first oligonucleotide which is common to each padlock probe in the set and a second oligonucleotide which is different for each padlock probe and represents a marker, wherein each marker comprises a binding domain separated into two parts, one at each end of the marker, and a detectable domain which gives rise to a detectable signal, and each marker in a set: (a) cannot bind to said nucleic acid domains simultaneously with another marker in the set; (b) comprises a different detectable domain that generates a signal that is distinguishable from the signal of another marker in the set; and (c) is present in a different amount in a pre-defined ratio such that each marker is capable of detecting the analyte at a range of concentrations that differs from the range of concentrations detectable by other markers in the set; (iii) allowing said padlock probes to bind to said nucleic acid domains such that the respective ends of each oligonucleotide of a padlock probe are brought into juxtaposition for ligation and ligating the juxtaposed ends such that each padlock probe is ligated to produce a circular oligonucleotide; (iv) subjecting the circular oligonucleotides to rolling circle amplification primed by one of the nucleic acid domains; and (v) detecting said signal from the RCA product. (i) contacting said sample with at least a pair of proximity probes each comprising a proteinaceous target-binding domain coupled to a nucleic acid domain and allowing the proximity probes to bind, in proximity, to their respective target, said target being either the analyte or a binding partner for the analyte; (ii) further contacting said sample with a set of at least two padlock probes, wherein each padlock probe comprises two oligonucleotides, each oligonucleotide being capable of binding to the nucleic acid domains of at least the said pair of proximity probes such that the respective ends of the oligonucleotides of each padlock probe are brought into juxtaposition for ligation when said proximity probes have bound to their target in proximity, a first oligonucleotide which is common to each padlock probe in the set and a second oligonucleotide which is different for each padlock probe and represents a marker, wherein each marker comprises a binding domain separated into two parts, one at each end of the marker, and a detectable domain which gives rise to a detectable signal, and each marker in a set: (a) cannot bind to said nucleic acid domains simultaneously with another marker in the set; (b) comprises a different detectable domain that generates a signal that is distinguishable from the signal of another marker in the set; and (c) is present in a different amount in a pre-defined ratio such that each marker is capable of detecting the analyte at a range of concentrations that differs from the range of concentrations detectable by other markers in the set; (a) cannot bind to said nucleic acid domains simultaneously with another marker in the set; (b) comprises a different detectable domain that generates a signal that is distinguishable from the signal of another marker in the set; and (c) is present in a different amount in a pre-defined ratio such that each marker is capable of detecting the analyte at a range of concentrations that differs from the range of concentrations detectable by other markers in the set; (iii) allowing said padlock probes to bind to said nucleic acid domains such that the respective ends of each oligonucleotide of a padlock probe are brought into juxtaposition for ligation and ligating the juxtaposed ends such that each padlock probe is ligated to produce a circular oligonucleotide; (iv) subjecting the circular oligonucleotides to rolling circle amplification primed by one of the nucleic acid domains; and (v) detecting said signal from the RCA product.