We can even peer into our own collective past and discover how the world smelled to our ancient ancestors. Case in point: We now know that the interiors of wealthy people's homes in Pompeii smelled woody and earthy, with a hint of citrus. A team of European researchers figured this very specific detail out by analyzing 2,000-year-old ancient incense burners. Finally, the researchers used gas chromatography and mass spectrometry to identify the molecular fingerprints of ancient resins, oils and other organic compounds. These could have served as fuel for the incense, but some may also have been offerings in their own right.