The microscopic roundworm Caenorhabditis elegans feeds on bacteria such as Pseudomonas aeruginosa. However, certain environmental conditions can cause P. aeruginosa to change in such a way that it becomes pathogenic -- that is, it sickens worms that eat it. In 2019, researchers in the Murphy lab showed that when worm mothers are made ill by P. aeruginosa, they learn to avoid the bacterium. Not only that, but their offspring, all the way down to their great-great grandchildren, somehow also know to avoid the bacterium. After four generations, though, the transgenerational avoidance behavior disappears, letting the worms return to feeding on the bacterium once more.