About 99% of Earth is uninhabitable; in deep underground places with high pressure and temperature, even the toughest bacteria cannot survive. However, there are places where life thrives, from tiniest toughest bacteria to the largest elephant. Then there are places that are habitable but are devoid of life; lava flows are a great example, as is the space between microbes. A new paper looks at these uninhabited yet habitable areas and considers what we may learn as we search for life in the universe.