What's fractional share trading? Here's how it works, and who's offering tiny slices of pricey stocks like Amazon and Shopify.

A wave of brokerage firms and fintechs have started allowing customers to trade small slices of individual stocks. Many are marketing the offering as a way to democratize investing and allow average customers to own popular but highly priced stocks.

It's all part of a fierce competition for young investors, especially high earners who could one day turn into lucrative wealth management clients.

We've been tracking the rollout of fractional share trading at startups and incumbents alike.

• December 2019: Robinhood is rolling out a way to buy $1 slices of stocks in a bid to lure first-time users. The launch comes after bigger rivals matched it on zero commissions.
• February 2020: Interactive Brokers has upended Wall Street time and again. Its cofounder explains how causing chaos is key to staying competitive in a cut-throat industry.
• February 2020: Robinhood, Fidelity, and Charles Schwab are racing to give customers the chance to buy $1 slices of stocks. We talked to a dozen insiders about who wins, who loses, and what it says about trading today.
• April 2020: Wells Fargo is eyeing even lower minimums for its robo-adviser as it looks to go head-to-head with Robinhood and Acorns
• May 2020: Charles Schwab is launching fractional stock-trading, making good on a promise that sent rivals Robinhood and Fidelity racing to offer slices of pricey shares

Firms invoke "democratization," the industry buzzword du jour, to describe the fractional trading feature. Startups and legacy players talk of leveling the playing field for all users regardless of whether they can afford a share of highly-priced stocks.

But companies have good reason to attract investors while they're still building wealth. For instance, they can lock in young customers with the hopes of cross-selling products to them down the line. And depending on how brokers clear the shares, fractional trading could offer another revenue stream after axing commissions to zero.

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