Trace gas spectroscopic detection has drawn much interest in recent years, as it both allows a better understanding of the molecular spectra of weak overtone transitions and in situ non-intrusive sensing of compounds at low concentration. However, recording a broadband spectrum within a very short measurement time and with high sensitivity remains a challenge. Now, scientists at the Max Planck Institute of Quantum Optics have recorded ultrasensitive absorption broadband spectra within tens of microseconds by combining cavity enhancement and frequency comb spectroscopy.