Congress is not known for working fast, but only a week after disclosing it an opened an antitrust investigation into big technology companies, a House committee will hold its first public hearing.

On Tuesday, the House Judiciary Committee’s panel on antitrust will begin its public dissection of the market power of massive tech companies like Facebook, Google, Amazon and Apple.

The focus in this first hearing is “the Free and Diverse Press,” according to the subcommittee’s hearing notice. There will be more hearings in the future.

The speed at which the House Judiciary Committee is moving to examine the business practices of these companies should not be an indication of quick action. Government antitrust inquiries take years before leading to any resolution.

The forced break-up of AT&T in 1984 began a decade earlier with a government antitrust lawsuit. Uncle Sam’s legal wrestling with Microsoft over bundling Internet Explorer with its Windows operating system lasted for years, and included a court-ordered break-up of the company, which was eventually reversed.

Investors in Facebook, Google’s parent company Alphabet and Amazon have felt the early heat of attracting such government public scrutiny. Shares of each of the companies fell at least 5% in the days after the House committee made its investigation public. The Congressional questions are in addition to separate Department of Justice antitrust probes of Google and Apple, and Federal Trade Commission examinations of Facebook and Amazon.

The size and influence of these companies already has become an issue in the 2020 presidential nomination race. Massachusetts Democratic Senator and presidential hopeful Elizabeth Warren bought a billboard in San Francisco declaring, “Break up big tech.”

This quartet of tech companies represents over 10% of the overall S&P 500. Their presence in the portfolio of global investors is eclipsed only by their omnipresence in the lives of consumers.