Three-nucleon (3N) short-range correlations (SRCs) are some of the most elusive structures in nuclei. Their observation and the subsequent study of their internal makeup will have a significant impact on our understanding of the dynamics of the superdense nuclear matter which exists at the cores of neutron stars. We discuss the kinematic conditions and observables that are most favorable for probing 3N SRCs in inclusive electronuclear processes and make a prediction for a quadratic dependence of the probabilities of finding a nucleon in 2N and 3N SRCs. We demonstrate that this prediction is consistent with the limited high-energy experimental data available, suggesting that we have observed, for the first time, 3N SRCs in electronuclear processes. Our analysis enables us to extract a3(A,Z), the probability of finding 3N SRCs in nuclei relative to the A=3 system.