This lecture delves into the early days of computer simulation, starting from the establishment of the Centre Européen de Calcul Atomique et Moléculaire in 1969. It covers the transition from Monte Carlo to Metropolis methods, the development of Molecular Dynamics, and the significance of the Metropolis method in high-energy physics. The presentation includes insights from Marshall Rosenbluth on the historical context and the evolution of Monte Carlo simulations. The lecture also explores the application of Monte Carlo schemes in computational molecular design and the analysis of electron dynamics. It concludes with a discussion on the impact of molecular simulations on scientific research over the decades.