 The caduceus trial of cardiosphere-derived cells, CDCs, has shown that it may be possible to regenerate injured heart muscle. The mechanisms of benefit are known to be indirect, but the mediators have yet to be identified. Here we pinpoint exosomes secreted by human CDCs as critical agents of regeneration and cardio protection. This article was authored by Ahmed Gamal El-Din Ibrahim, Kuching, and Eduardo Marvin.