Abstract: Syukuro MANABE and Klaus HASSELMANN share half of the 2021 Nobel Prize in Physics for "the physical modelling of Earth's climate, quantifying variability and reliably predicting global warming". The other half of the prize goes to Giorgio PARISI for "the discovery of the interplay of disorder and fluctuations in physical systems from atomic to planetary scales". The pioneering contributions of three scientists to the understanding of complex physical systems are introduced, and the opportunities and prospects of complexity science are prospected.