During an exhibition on the risks of smoking, two pig lungs are shown to a group of students, in order to explain the differences between a non-smoker's lung and a smoker's one. The lung on the left was artificially stained to give a realistic view of a human lung damaged by smoke.
<a href="//commons.wikimedia.org/w/index.php?title=User:AlfonsoLucifredi&amp;action=edit&amp;redlink=1" class="new" title="User:AlfonsoLucifredi (page does not exist)">Alfonso Lucifredi</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>