https://techcrunch.com/2019/12/12/robinhood-fractional-share/

One share of Amazon stock costs over $1700, locking out less wealthy investors. So to continue its quest to democratize stock trading, Robinhood is launching fractional share trading this week. This lets you buy 0.000001 shares, rounded to the nearest penny, or just $1 of any stock with zero fee.

The ability to buy by millionth of a share lets Robinhood undercut Square Cash’s recently announced fractional share trading, which sets a $1 minimum for investment. Robinhood users can sign up here for early access to fractional share trading.