Abstract: The history of nonlinear responses in physics is long and rich. Although they were first considered as early as 1968, only recently quadratic-in-electric-field corrections to Ohm’s law begun to regain attention. In the age of topology in condensed matter physics, it has been recognized that nonlinear responses can be triggered by nontrivial Berry curvature or quantum geometry in a system. This realization has led to significant experimental efforts and the discovery of giant nonlinear responses of 2D materials using both Hall-bar and disk-geometry samples. Microscopic theoretical calculations have shown an apparent discrepancy between the measured and calculated magnitudes of the effect — a phenomenon that remains not fully understood. In this talk, I will discuss contributions to second-order nonlinear transport in 2D materials that have not received adequate theoretical treatment and outline my work on building a microscopic theoretical framework to describe these phenomena.