This research explores how symbiotic fungi that help trees obtain nutrients coordinate their genes to develop different structures and functions. The study created a comprehensive gene activity map of the fungus Laccaria bicolor under various conditions to understand how it forms beneficial partnerships with tree roots. This knowledge helps us understand how forests maintain their health and productivity. Impacts on everyday life: • Better understanding of how forests naturally maintain their health and growth • Potential applications for improving tree growth in forestry and agriculture • Insights into how organisms adapt to different environmental conditions • Contribution to sustainable forest management practices • Better understanding of beneficial plant-microbe relationships that could be applied to crop production