The critical step for development of all-solid-state lithium metal batteries lies in revealing the origin of lithium dendrite formation in the electrolyte. In article number 1902123, Yun Song, Dalin Sun and co-workers use the representative electrolyte, LiBH4 to demonstrate that lithium dendrites directly form inside the bulk solid-state electrolyte, which is like the process in which plants break through a soil bed and rise into the air.