The invention provides compositions and methods for the detection of targets in a sample; in particular, an immunohistochemistry (IHC) sample. Probes and detectable labels may be provided in multiple layers in order to increase the flexibility of a detection system, and to allow for amplification to enhance the signal from a target. The layers may be created by incorporating probes and detectable labels into larger molecular units that interact through nucleic acids base-pairing, including peptide-nucleic acid (PNA) base-pairing. Optional non-natural bases allow for degenerate base pairing schemes. The compositions and methods are compatible with immunohistochemistry (IHC), but also could be used in immunocytochemistry (ICC), in situ hybrid.