Standard Big Bang Nucleosynthesis (BBN) predicts a primordial helium-4 mass fraction (Yp) of approximately 0.2471, with very tight constraints based on the baryon-to-photon ratio measured from the CMB and the physics of light element formation in the first few minutes after the Big Bang. However, high-precision observations of metal-poor extragalactic HII regions and blue compact dwarf galaxies suggest a primordial helium-4 abundance that is systematically offset from the BBN prediction, with some measurements yielding values that are either slightly higher or slightly lower than expected, depending on the analysis method and systematic corrections applied (Izotov et al. 2014; Aver et al. 2015). Lambda-CDM struggles to reconcile these discrepancies because BBN is one of its cornerstone predictions, and any deviation requires either modifying fundamental physics during nucleosynthesis (such as changing the number of neutrino species, the neutron lifetime, or the expansion rate) or invoking unknown systematic errors in the observations. A shift in the helium-4 plateau challenges the internal consistency of Lambda-CDM, as the same baryon density that fits the CMB must also fit BBN, and any mismatch suggests either the early universe was more complex than assumed or that the observations are contaminated by astrophysical processes.