Chronicles social media over two millennia, from papyrus letters that Cicero used to exchange news across the Empire to today, reminding us how modern behavior echoes that of prior centuries and encouraging debate and discussion about how we'll communicate in the future.

Introduction: Cicero's web -- The ancient foundations of social media: why humans are wired for sharing -- The Roman media: the first social-media ecosystem -- How Luther went viral: the role of social media in revolutions (1) -- Poetry in motion: social media for self-expression and self-promotion -- Let truth and falsehood grapple: the challenges of regulating social media -- And so to the coffeehouse: how social media promotes innovation -- The liberty of printing: the role of social media in revolutions (2) -- The sentinel of the people: tyranny, optimism, and social media -- The rise of mass media: the centralization begins -- The opposite of social media: media in the broadcast era -- The rebirth of social media: from ARPANET to Facebook -- Epilogue: History retweets itself.