Pressures above 1 Mbar, equivalent to energy densities stored in chemical bonds, are predicted to severely reshape the periodic table of the elements as we know it. Such extreme conditions can radically alter the electronic structure and chemical properties of materials, especially when heating these to temperatures of several thousand kelvins, which suggests new approaches for the synthesis of so-far unknown material structures and compounds. However, due to a lack of predictive modelling and experimental challenges, exploration and exploitation of new chemistry above one megabar has remained a dark spot in our understanding of matter. Unprecedented experimental capabilities provided by large-scale laser facilities and X-ray free electron lasers, also supported by new theoretical and computational tools, now drastically change this situation and I am at the forefront of these revolutionary developments. With MEGACHEM, I will establish the research direction of dynamic megabar chemistry, motivated by my pioneering studies on light elements mixtures. Performing exploratory experiments in close interplay with theory, I will investigate novel routes to two interlinked “holy grail” cases: a) the synthesis of the long sought but still speculative BC-8 structure of carbon and b) a new approach to an efficient formation of ultrasmall nanodiamonds of tailored size and dopant level. Indeed, for reaching both goals, the pressure-driven insulator-metal transition of liquid hydrogen may play a central role. By investigating these cases, MEGACHEM will cover new ground and test state-of-the-art theoretical models by combining studies at my university labs with experiments at large-scale research infrastructures: hard X-ray free electron lasers such as the European XFEL, and the largest optical laser systems, such as the National Ignition Facility and the Extreme Light Infrastructure. By doing so, MEGACHEM can impact various areas, ranging from astrophysics to photocatalysis.