Plants, algae and cyanobacteria are the only organisms capable of producing their food while performing photosynthesis. By employing complex biophysical processes, which act on multiple temporal and spatial scales, they perform highly efficient energy converting reactions. The basic machinery behind these reactions consists of two parts: the photosynthetic electron transport chain (PETC) and the Calvin-Benson-Bassham (CBB) Cycle. The photosynthetic activity is driven by the light availability at the site of the PETC and is pulled by the energy demand on the CBB site. Hence, the photosynthetic system can, and in fact, should be treated as an integrated supply-demand system [1]. During this talk, I will present our most recent mechanistic model of photosynthesis [2] developed for C3 plants to study the dynamics of balancing the energy supply under stress. Next, thanks to the modular construction of our computational models, I will show how a highly simplified version of PETC model could guide us to gain a better understanding of the dynamics of photosynthesis in diatoms [3]. Finally, I will present the preliminary results on our most recent work on capturing photosynthesis in cyanobacteria. Most recent publications: [1] Matuszyńska et al. [2019] Physiologia Plantarum https://doi.org/10.1111/ppl.12962 [2] Saadat et al. [2021] Front. Plant Sci., 12:750580 https://doi.org/10.3389/fpls.2021.750580 [3] Seydoux et al [2022] bioRxiv, accepted to New Phytologist https://doi.org/10.1101/2021.09.06.459119