This paper reviews various mechanisms for generating large primordial fluctuations and their implications for the production of primordial black holes (PBHs) and scalar-induced secondary gravity waves (SIGWs). The authors aim to understand the impact of loop corrections on quantum correlations and the power spectrum. They provide a comprehensive review of the standard model of the universe, including causal structure, inflation, quantization of primordial perturbations, and field-theoretic techniques such as the "in-in" formalism. The paper discusses the severe constraints on PBH production in single-field inflation due to renormalized quantum loop corrections and explores methods to circumvent these constraints in Galileon inflation, multiple sharp transition (MST)-induced inflation, and stochastic single-field inflation using effective field theory (EFT) frameworks. The analysis covers dynamical renormalization group (DRG) resummation, adiabatic and late-time renormalization schemes, and their application to solar and sub-solar mass PBHs. The paper also discusses the production of SIGWs in MST setups and Galileon inflation, and addresses the issue of overproduction of PBHs. Finally, the paper concludes with a detailed discussion on the implications of large fluctuations and the impact on PBH formation and SIGWs.This paper reviews various mechanisms for generating large primordial fluctuations and their implications for the production of primordial black holes (PBHs) and scalar-induced secondary gravity waves (SIGWs). The authors aim to understand the impact of loop corrections on quantum correlations and the power spectrum. They provide a comprehensive review of the standard model of the universe, including causal structure, inflation, quantization of primordial perturbations, and field-theoretic techniques such as the "in-in" formalism. The paper discusses the severe constraints on PBH production in single-field inflation due to renormalized quantum loop corrections and explores methods to circumvent these constraints in Galileon inflation, multiple sharp transition (MST)-induced inflation, and stochastic single-field inflation using effective field theory (EFT) frameworks. The analysis covers dynamical renormalization group (DRG) resummation, adiabatic and late-time renormalization schemes, and their application to solar and sub-solar mass PBHs. The paper also discusses the production of SIGWs in MST setups and Galileon inflation, and addresses the issue of overproduction of PBHs. Finally, the paper concludes with a detailed discussion on the implications of large fluctuations and the impact on PBH formation and SIGWs.