This book is about changing corporate power structures. Over the last two decades, we have seen a distinct transformation of the 'C-suite'- a term denoting the most important senior executives in an organization - characterized by the proliferation of and variation in new Chief X Officer (CXO) roles, in which X stands for a specific domain such as sustainability, communication, digital, human resources, finance, or many alternatives. By exploring the emergence and evolution of these CXO positions, the authors examine the evolving ways in which power at the apex of complex organizations is structured through roles and relationships, in anticipation of and in response to diverse contingencies and interests. The book develops a theoretical account, combined with a rich empirical illustration, of the C-suite's transformation to enhance our understanding of these elites' new command posts, sources of expertise and identity, competition and collaboration, and ways of getting things done. In doing so, it extends the political perspective of organizations which has largely overlooked the changing design of executive power and the action means of senior executives, who have more leeway to construct their roles than managers at any other organizational layer. It is in moments of structural transformations, such as the ongoing incorporation to executive committees of a plethora of new CXO roles, that the political model of organizations is better revealed and assessed.