This book analyses the reasons why cycling is returning to cities around the world as an essential element in solving and overcoming the crisis of the dominant car-centric model of urban mobility, with its known adverse consequences of congestion, pollution and urban space consumption. It argues that it is not possible to solve this crisis without giving a central role to the bicycle, both as a mode of transport in itself and as an integrating and cohesive element of other forms of transport. The bicycle, due to its special characteristics of autonomy, simplicity and energy efficiency, must be.