Plants are able to recognize even small changes of surrounding temperatures to optimize their growth and development. At warm temperatures, plants exhibit diverse architectural adjustments, including hypocotyl and petiole elongation, leaf hyponasty, and reduced stomatal density. However, it was unknown until recently how warm temperatures affect the early stages of seedling development. In our recent study, we demonstrated that the RNA-binding protein FCA is critical for sustaining chlorophyll biosynthesis during early seedling development, which is a prerequisite for autotrophic transition, at warm temperatures. FCA plays dual roles in this thermal response. It inhibits the rapid degradation of protochlorophyllide oxidoreductases (PORs) that mediate chlorophyll biosynthesis. In addition, it induces the expression of POR genes at a chromatin level, which contributes to maintaining functional levels of the enzymes. Our findings provide a first molecular basis for the thermal adaptation chlorophyll biosynthesis during early stages of seedling development in nature.