The experiment has been a while since it came out, but it is so fascinating and exciting that I have to post about it. It is basically about an experiment done by Richard Lenski with bacterias that could only eat glucose, and after 20 years, around 40,000 generations, they could eat ascorbate. That is amazing! It is a big leap. According to the paper, three mutations had to occur. After this one mutation around generation 20,000, they found out it made it easier for the bacterias to mutate into ascorbate eating ones. They did it by freezing bacterias every some generations and reviving them to repeat it.
And if you want to look at the abstracts and summary by the author himself: https://myxo.css.msu.edu/ecoli/