Only a few decades ago, the practice of improvisation could still have been described as a neglected topic in much of the literature on the arts and philosophy; but since then matters have changed significantly. The role of improvisation in the arts, primarily in music and the performing arts such as dance and theater is now widely recognized. Of course, the debate on the aesthetics of improvisation and on the ethical and political issues connected to it is lively and not limited to the topic of artistic creativity. The number of philosophical studies dedicated to improvisation in various artistic practices and disciplines is growing rapidly, and it is not possible to offer here a complete survey of the literature. Improvisation is a kind of agency that is structured and, at the same time, capable of adapting to changes in its surroundings. The chapter also presents an overview of the key concepts discussed in this book.