Molecular beacons, targeted molecular probes built to recognize and bind to a specific DNA sequence of interest, at which point they fluoresce. A molecular beacon can be tailored to recognize virtually any DNA sequence, making this technology a versatile tool in many medical and scientific pursuits. This illustration depicts a molecular beacon (white) that has been attached to a transfer RNA molecule (grey-green). The blue structure represents a nascent strand of messenger RNA, produced by an activated gene, that has been recognized and bound to by the molecular beacon.