There has always been a whiff of world domination to the aspirations of big tech companies: to become a platform for everyone on Earth, to be the “everything store,” to organize the world’s information. Yet as Facebook, Amazon, Google, and others reach unprecedented scale, regulators, activists, academics, and politicians are starting to wonder how big is too big. Lately, there are even signs of growing bipartisan recognition that something should be done, whether it’s Sen. Mark Warner’s detailed proposal for regulating social networks or Sen. Orrin Hatch’s request, following President Trump’s angry and confusing tweets, that the Federal Trade Commission investigate potential anti-competitive practices by Google.

Past antitrust cases provide clues about how lawmakers might proceed, but today’s tech giants pose some novel questions. Are laws made to rein in railroads effective regulatory tools for digital networks? What is the harm, exactly, when products are cheaper or even free? How does the ability of gigantic platforms to acquire or crush any rival affect the economy and society? How do you regulate a company that’s becoming something more akin to an infrastructure?

This week, The Verge is looking at different aspects of the monopoly debate, from the last big tech antitrust battles in the ‘90s to overlooked markets like prison phones to how the anti-monopoly cases against today’s giants might be built.