Stable internal combustion (IC) engine operation with a lean mixture allows improved thermal efficiency and reduced engine-out emissions. However, lean limits in IC engines are challenging due to poor ignitibility. Narrow throat pre-chamber as an ignition source allows extending the lean limit through a robust multi-reactive jet ignition and in-cylinder turbulence generation. These benefits have revived the research interest in such narrow throat configurations of pre-chamber. Metal engine studies offer limited insights into the physics of pre-chamber combustion (PCC). However, when coupled with recent optical engine studies involving high-speed visualization and laser diagnostics, a better understanding of this combustion mode is unlocked. This work attempts to evaluate and summarise the recent advancement in PCC research.