Minecraft wiki entry for Glow_Lichen, associated text: "And yes, Glow Lichen is the new cave light source I mentioned in the cave prototype video a while back. We made them mainly for the not-yet-released larger caves. Glow Lichen generate naturally, but you can also grow it yourself and make eerie glowing cave paths :)" – @henrikkniberg on Twitter, January 20, 2021