The tech giants are too big. Other than Donald J. Trump, that’s the defining story of 2017, the meta-narrative lurking beneath every other headline.

The companies I call the Frightful Five — Amazon, Apple, Facebook, Microsoft and Alphabet, Google’s parent company — have experienced astounding growth over the last few years, making them the world’s five most valuable public companies. Because they own the technology that will dominate much of life for the foreseeable future, they are also gaining vast social and political power over much of the world beyond tech.

Now that world is scrambling to figure out what to do about them. And it is discovering that the changes they are unleashing — in the economy, in civic and political life, in arts and entertainment, and in our tech-addled psyches — are not simple to comprehend, let alone to limit.

I’ve spent the last few years studying the rise of these giants. As tensions over their power reached a high boil this summer — Facebook and Russia, Google and sexism, Amazon and Whole Foods — I began thinking more about the nature and consequence of their power, and talking to everyone I could find about these companies. Among them were people in the tech industry, as well as many in other power centers: Washington, Hollywood, the media, the health care and automotive businesses, and other corners of society that may soon be ensnared by one or more of the Five.