Nano Cap
Small public companies having a market capitalization below $50 million.
Investopedia Commentary
This is as small as you can get! Nano caps are very risky because they are such small companies.
Keep in mind that classifications such as "large cap" or "small cap" are only approximations that change over time. Also, the exact definition of the various sizes of market cap can vary between brokerage houses.
Related Links
Introduction to Small Caps
What Is A Small Cap?
The Great Gap
Market Capitalization Defined
See also: Large Cap, Market Capitalization, Mega Cap, Micro Cap, Mid Cap, Small Cap
Also spelled: nano-cap, nanocap