Spaceflight alters the pattern of chemical tags that adorn DNA in plant seedlings. Weiming Cai and colleagues from the Shanghai Institute of Plant Physiology and Ecology, China, profiled the genome-wide epigenetic patterns of Arabidopsis thaliana seedlings that spent 60 h in the microgravity of low Earth orbit aboard the Shijian-10 recoverable satellite. They analyzed the distribution of methyl tags across the genome — an epigenetic mark that affects gene expression levels — and found that seedlings exposed to microgravity had lower methylation on average than control plants grown on the ground, although certain genes related to methylation, transcription factors and hormones tended to be more methylated. Epigenetic differences were also observed among genes involved in cell-wall modification and in transposable elements. The findings could help inform the design of plants optimized for growth in space.