An appearing, disappearing tattoo inkNature: Watch this invisible tattoo appear under UV light04:13 How the epigenome could help explain why big dogs age fasterNature: Big dogs age faster than little ones — rogue ‘jumping genes’ might be to blameSubscribe to Nature Briefing, an unmissable daily round-up of science news, opinion and analysis free in your inbox every weekday. Hosted on Acast. See acast.com/privacy for more information.