A new data acquisition software is now available for the PicoHarp 300 Time-Correlated Single Photon Counting system from PicoQuant. The version 2.3 provides a new real-time correlator for Fluorescence Correlation Spectroscopy that calculates two autocorrelations and the cross correlation between two photon streams simultaneously. The PicoHarp is based on an entirely new time digitizer with 4 picoseconds resolution, a very short dead time, a processing rate of up to 10 million counts per second, and an extremely low differential non-linearity. The new software is provided free of charge to all owners of a PicoHarp 300.