The Eocene/Oligocene transition in universally regarded as a pivotal phase in Earth's history, at the core of the 'greenhouse'/'icehouse' transition, and the first formation of major Antarctic icesheets. Yet, recent studies have indicated a distinct 'two step' nature of this transition, straddling ~400 kyr. Both of these steps are marked by d18O and reconstructed SST changes (Ca/Mg, TEX, Alkenones) but it is debated how much of the change can be attributed to ice volume, and how much to temperature. Moreover, processes underlying these changes are even more debated. We encourage a wide range of contributions that provide new insight into the complex series of global climatic changes spanning the E/O transition.