The EarthCARE (Earth Cloud, Aerosol and Radiation Explorer) satellite is a joint ESA–JAXA mission that was launched on 28 May 2024; it carries a Doppler cloud profiling radar (CPR), a high-spectral-resolution atmospheric lidar (ATLID), a multi-spectral imager (MSI), and a broadband radiometer (BBR). A large number of cloud, aerosol, precipitation, and radiation data products will be produced, some derived from individual EarthCARE instruments and some from the synergy of multiple instruments. This collection of papers describes the theoretical basis for the EarthCARE Level 2 algorithms and provides a prelaunch evaluation of their performance. An innovative aspect that links a number of the papers together is the use of realistic 3D test scenes, 6000 km in length, with cloud, precipitation, and aerosol fields from a high-resolution cloud-resolving model and an aerosol transport model, with which observations by the four EarthCARE instruments have been simulated using state-of-the-art instrument simulators. This approach has enabled these algorithms to be evaluated and compared using a common dataset. The special issue is limited to papers describing official ESA or JAXA retrieval algorithms and their evaluation as well as several closely related papers.