In this video as part of The Motley Fool's "Ask a Fool" series, Fool health-care analyst David Williamson takes a question from a Fool reader, who writes, "What's your Foolish opinion on Organovo (NASDAQ:ONVO)? Buy, sell, or hold?"

David introduces investors to the company, which is working to develop the ability to use 3-D printing technology to create human livers, which would facilitate medical testing for liver toxicity without having to test on actual humans. David also warns that even though this is a potentially disruptive force, it's still so early in the development of its product that there's still a lot of risk for investors here, and he advises keeping this as no more than a tiny percentage of any investment portfolio.

David Williamson and The Motley Fool have no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.