Diatoms are among the most successful life forms on Earth, having taken over a substantial role in regulating the global oxygen balance and climate that other microalgae maintained for nearly a billion years. Their ecological and evolutionary success has made diatoms dominant and diverse, yet the mechanisms behind this success remain poorly understood. This Swiss National Science Foundation – Ambizione project (https://data.snf.ch/grants/grant/233303) addresses this question and investigates the role of adaptive radiation and associated key innovations in the evolution of freshwater diatoms. By integrating morphology, physiology, genomics, transcriptomics, and computer-based modeling of a newly discovered diatom assemblage of the genus Diploneis living in the African Lake Tanganyika, the adaptive nature of their rapid diversification will be investigated and whether specific morphological (i.e. glass shell ornamentation) and physiological (i.e. sterols) innovations triggered it. Species collection and cultivation, as well as microscopic, genetic, and experimental work in the laboratory, will be used to link evolutionary traits to their genetic basis and ecological functions, thereby revealing the contribution of adaptive radiation to the evolution and success of these tiny, ubiquitous protagonists that produce the oxygen we breathe and stabilize the climate in which we live.