SensL (Blackrock, Ireland) has developed the PCDMini, a miniature photon counting system for applications in biosciences, astronomy, and remote sensing. The PCDMini is a printed circuit board with hermetically sealed detector. The basic unit features quenching architecture and is available with a number of optional snap-on modules for enhanced functionality including a Peltier cooler driver to enable operation down to -20 °C, and a PC control interface with integrated counter featuring 1,000 updates a second counting. SensL’s silicon photon counting sensors are based on a shallow junction Geiger-mode avalanche photodiode. This offers increased sensitivity to blue-red wavelengths, increased response time to fast optical signals, and low internal operating voltages. These performance characteristics make the mini photon counter useful for biomedical applications such as the capture of fast fluorescence decay signals.