Light generated by broadband nonlinear mixing demonstrates two-photon correlation on the classical and quantum mechanical levels. I will describe two experiments that precisely measure the broadband two-photon correlation of light generated by both three waves mixing (TWM) and four waves mixing (FWM), demonstrating novel effects in the high power (classical) and low power (quantum) regimes. In the first experiment, a photonic crystal fiber is pumped with narrowband picosecond pulses to produce FWM in a unique regime, where extremely broadband sidebands (>100nm) are generated that are totally incoherent, yet time-energy correlated. We measure the time-energy correlation using sum-frequency generation as an ultrafast correlation detector and demonstrate a unique power dependent splitting of the correlation in both energy and time. In the second experiment ultra-broadband entangled photon pairs are generated by parametric down conversion. The bi-photon wave-function is measured in both amplitude and phase through quantum two-photon interference. I will present a theoretical framework accounting for the observations, and illustrate the differences between broadband FWM and TWM. Both the quantum and the classical aspects of the measured correlations will be discussed.