Photosynthesis is the biological process in which solar energy is converted into chemical energy. The energy is then used to produce organic molecules from carbon dioxide. The key reactions of photosynthesis occur in plants, algae and cyanobacteria in two complex structures, the photosystems. While it is well known that the functional photosystems reside in a special membrane system, the thylakoids, many details of their molecular assembly and the insertion of the proteins into the membranes have remained unknown. A surprising discovery now published in Nature Plants (07 September 2020) demonstrates that it is not the pre-synthesized protein that is transported to the thylakoid membranes for photosystem assembly. Instead, the mRNAs encoding core proteins of the photosystems are transported to the thylakoid membranes in a ribosome-independent process. The findings contribute to a developing concept that mRNA molecules can provide much more than just the sequence of the protein: in this case they also carry signals that seem to control the location and co-ordination of photosystem assembly. The identification of two proteins likely involved in this process by interacting with these mRNAs opens the road towards the detailed understanding of the molecular mechanisms involved. These results have been obtained in an international cooperation between Cyanolab (special congratulations to Luisa and Matze!), Annegret Wilde (Bacterial Genetics Freiburg), Satoru Watanabe (Tokyo, Japan) and was led by the former FRIAS fellow Conrad Mullineaux (Queen Mary University of London, UK). We are grateful for support by the DFG-funded Graduate School 2344 “MeInBio – BioInMe: Exploration of spatio-temporal dynamics of gene regulation using high-throughput and high-resolution methods“.