Researchers from Virginia Tech and the Chinese Academy of Sciences have described some billion-year-old fossils that they interpret as green algae. What’s interesting about these fossils, aside from being older than previously known green algal fossils, is that they appear to be fully multicellular, with differentiated cells. This is a valuable find, because it shows that at least one of the many green algal lineages that have independently evolved multicellularity did so relatively early. Sadly, the article, in Nature Ecology & Evolution, is paywalled. The best I can do is link to the article’s page on ResearchGate, which has a read-only version. I requested a full-text through that page, and the lead author sent a pdf promptly.