How do enzymes evolve? Natural selection has produced molecular catalysts with amazing performance; some enzymes can accelerate the rate of chemical transformations by factors of 106 up to 1017. Why is this process, which is based on ‘trial and error’ so rapid and efficient? We cannot examine the ‘fossils’ of the protein world, but we have recently gained access to the frozen ‘fossilized’ record of an evolved bacteria. In collaboration with A/Prof Cooper (University of Houston), this study deciphers (structurally and functionally) the evolution of E. coli pyruvate kinase as the bacterium adapts to various energy limiting environments. Because we can reproduce protein evolution in the laboratory and in real time, implementing the principles of Darwinian evolution to individual genes and enzymes, we can get a glimpse of the evolutionary intermediates, routes, and mechanisms, that may have led the way to the highly proficient enzymes known to us today. The ability to evolve proteins in the laboratory is also a powerful mean of engineering novel bespoke enzymes for a range of applications, for instance aiding synthetic organic chemistry.