Recently, there has been growing interest in electronic systems that exhibit both strong spin-orbit coupling and strong electron correlations. These systems combine two central threads of modern quantum materials research: correlated electron physics that underlies phenomena such as high-Tc superconductivity, and spin-orbit physics that describes systems such as topological insulators. When these two interactions compete at the same energy scale in a material, fundamentally new quantum phenomena have been predicted to emerge. Recently, an experimental platform with this rare interaction regime has been realized for the first time in 5d transition metal oxides such as iridium oxides. In this talk, I will focus on one specific member of this family Sr2IrO4 that has received much attention due its striking similarities to the cuprate high-Tc superconductors. I will describe a new nonlinear optical spectroscopy technique that enabled us to find an unusual hidden magnetic ordered phase in the Sr2IrO4 system. I will discuss the potential relevance of this novel phase to superconductivity in both iridates and cuprates.