What just happened? Google, Amazon, Facebook, and Apple have all received letters requesting sensitive information, as well as over 400 questions from the House Judiciary Antitrust Subcommittee about how their businesses achieved dominant positions in their respective industries. They mostly touch on controversies that journalists have been writing about for years, but now there's a chance we may see exactly what has led to a handful of companies becoming almost too big to fail.

House lawmakers recently sent letters to four of the biggest tech companies asking for internal documents, emails, and other closely guarded information. The formal request was made as part of an ongoing antitrust investigation into Google, Amazon, Facebook, and Apple, also known as GAFA. The companies have until October 14 to respond, but it's worth noting this isn't a subpoena.

Specifically, the bipartisan House Judiciary Subcommittee wants GAFA to share detailed information about how their businesses operate -- including financial data on their products and services, as well as internal records about merger discussions and targets, competitors, market research, and "key business decisions." Furthermore, the companies are asked to provide documents on any past antitrust investigations.

The four letters could reveal if the Big Four reached their dominance in search, e-commerce, social media, and other markets through anticompetitive practices. Further, they name over 50 executives at these companies, which are now under lawmakers' microscope to determine whether they've been aware or been part of any wrongdoing.

Rep. Jerrold Nadler said in a statement that "there is growing evidence that a handful of corporations have come to capture an outsized share of online commerce and communications." The regulators want to use the requested information to see how the Congress should respond, should any of these companies be found liable of "using their market power in ways that have harmed consumers and competition."

The Google letter asks its parent company, Alphabet, to send over internal records and communications related to several mergers and acquisitions, including DoubleClick, AdMob, YouTube, Android, as well as attempts to purchase Vevo. Regulators also want to know about Google deals with Android OEMs, how its search algorithm works with respect to its own services and those of its rivals, and whether it has removed apps from the Play Store that competed in the same categories as Google apps.

Amazon is asked to provide insight into how its algorithm ranks various products offered by the own company as well as competitors', and into how it decides on the price for the products it sells. As with Google, regulators want to know more about Amazon's acquisitions, including Zappos, Whole Foods, Sizmek, Ring, Blink, Audible, and several others. There's also a request for details about Amazon's negotiations with book publishers and whether it ever used its search algorithm as a way to coerce a publisher to sign a specific deal.

In the case of Facebook, Congress wants to know more about the company's acquisition of WhatsApp and Instagram as well as VPN provider Onavo, which was reportedly used to collect data on its users and inform on the social giant's many purchases. Facebook will have to compile documents about the decision making process on everything related to the social graph. Interestingly, this comes after a British parliamentary committee revealed last December through leaked documents and emails that Facebook has been giving preferential access to user data for partners like Netflix and Lyft while cutting off competitors like Vine.

The Apple letter asks for information on well-known issues such as the company's decision to remove parental control and screen-time apps from the App Store, the way its App Store algorithm works, revenue sharing practices for in-app purchases and subscriptions, and "Sherlocking" of functionality from third-party apps like Clue and SwiftKey. Pretty much all the requests have to do with the company's restrictive business practices, including the controversies around battery replacements and third-party repairs.