Summary:

• **Ancient Tooth Blackening in Vietnam**: Scientists discovered that people in Vietnam were blackening their teeth on purpose about 2,000 years ago, which is much older than anyone thought before. They found evidence of this practice by studying old teeth that were dug up from ancient burial sites.

• **How and Why They Did It**: Researchers believe Vietnamese people used a special black substance to coat their teeth, similar to how people today might wear makeup or nail polish. This was likely a sign of beauty and status in their society, showing that people have cared about how they look for thousands of years.