This document discusses vulnerable plaque and the history of research on plaque vulnerability. It provides definitions of vulnerable plaque and different types of vulnerable plaque such as rupture-prone plaques. The document outlines pioneers in plaque research and emerging techniques for detecting vulnerable plaque both invasively, such as intravascular ultrasound (IVUS) and optical coherence tomography (OCT), and non-invasively using magnetic resonance imaging (MRI). It summarizes the natural history of vulnerable plaques and their role in acute coronary events.