A deep dive into macroalgae genetics has uncovered the genetic underpinnings that enabled macroalgae, or 'seaweed,' to evolve multicellularity. Three lineages of macroalgae developed multicellularity independently and during very different time periods by acquiring genes that enable cell adhesion, extracellular matrix formation, and cell differentiation, researchers report. Surprisingly, many of these multicellular-enabling genes had viral origins. The study, which increased the total number of sequenced macroalgal genomes from 14 to 124, is the first to investigate macroalgal evolution through the lens of genomics.