As far back as 2015, visitors to Washington, D.C., would have seen black grime covering the Jefferson Memorial. But over the last few years, a restoration project has taken place to clean the 82-year-old monument.
After some research into what was causing the mysterious growth, biofilm was found to be the problem. Biofilm is a thin, slimy complex structure of bacteria, fungi, and algae that can adhere to various surfaces.
