Viruses can evolve fast and sometimes adapt quickly to a new host species. For example, an influenza virus that normally infects birds can become adapted to humans. The tobacco etch virus normally infects tobacco plants. Professor Santiago Elena from Valencia wants to find out what it takes to make the tobacco virus capable of infecting another plant: Arabidopsis. Durting the evolutionary experiment we see that after 30 rounds of experimental evolution the virus is indeed adapted to the new host plant! The new virus adapted to Arabidopsis has three mutations at the genetic code, when compared to the normal (tobacco loving) virus.