In photometry (the measurement of light), catching individual microwave photons was long impossible: their energy is on par with the thermal jitter of atoms. The breakthrough came from superconductors: a single photon sets off an avalanche, like a snowball rolling downhill gathers more snow, a microwave quantum gives birth to dozens of its kind. The amplified signal is separated from the background by analyzing quantum entropy — a measure of disorder: a photon avalanche has a distinct entropy compared to random noise. The detector is cooled nearly to absolute zero to suppress thermal interference. Efficiency reaches 84.5% with minimal errors. The paradox: catching particles from the Universe's fiery past requires extreme cold. Such detectors will link quantum computers and, perhaps, allow us to register photons from the echo of the Big Bang, testing the standard model of physics.