Why does the announcement of a new cellphone model ignite excitement and passion? Why do most people return home when they forget their cellphones, while only few would return for their wallets? How did the cellphone technology become so dominant for many of us? This book offers an analysis of the historical evolution and of the meanings of this technology in the lives of billions of people. The book offers a unique point of view on the cellphone that merges genealogical analysis of its development since the 1990s and philosophical insights into a coherent analytical framework. With new concepts like "histories of the future" and "memory prosthesis," the book aims to explain the excitement arising from new model announcements and the ever-growing dependency on the cellphone through the framing of these experiences in wide philosophical contexts. It is the first philosophical analysis of the important roles the cellphone plays in contemporary everydayness.