The present invention provides nucleic acid hybridization probes having a target-binding region and a labeled hairpin structure at at least one end of the probe. The hairpin-labeled probes include oligonucleotides, dendrimers, and primer-extended nucleic acids. The probes can be used in disclosed methods for detection of target nucleic acids. In addition, the oligonucleotide probes can be used in disclosed methods for primer-extension, including, e.g., random priming and PCR amplification, to produce the primer-extended hairpin-labeled probes. Also disclosed are kits comprising the hairpin-labeled oligonucleotide and dendrimer probes. Further, the present invention provides biomolecules (e.g., peptides, polypeptides, carbohydrates, lipids, and the like) that are labeled via linkage to labeled hairpin structures.