A unimolecular probe for hybridization to a molecule comprising a target nucleic acid sequence, the probe includes: a first nucleic acid sequence complementary to the target sequence (target-binding sequence); a second nucleic acid sequence complementary to a portion of the first nucleic acid sequence and capable of hybridization therewith to form a first intramolecular duplex. In use, the target and target-binding sequence hybridize to form a duplex. A probe can be used to detect a molecule containing the target sequence, act as a primer for synthesis or amplification, etc.