A nanobe (/ˈnænoʊb, ˈneɪnoʊb/) is a tiny filamental structure first found in some rocks and sediments. Some scientists hypothesize that nanobes are the smallest form of life, 1/10 the size of the smallest known bacteria. No conclusive evidence exists that these structures are, or are not, living organisms, so their classification is controversial. The smallest are just 20 nanometers in diameter. Some researchers believe that these structures are crystal growths, but the staining of these structures with dyes that bind to DNA might indicate that they are living organisms.