Targeted and regular studies of diatoms in the sediments of Lake Ladoga started in the late 1950s as part of the work of the Integrated Ladoga Expedition of the Institute of Limnology of the Russian Academy of Sciences. The main directions of studying diatoms in Ladoga sediments were outlined and developed during the major part of the reviewed period by Dr. Natalia N. Davydova (1931–2014). She studied the systematic, ecological, and geographical composition of diatoms in the surface sediments and sediment cores retrieved from the Ladoga bottom, described the main stages of Lake Ladoga evolution in the Late Glacial-Holocene period based on diatom analysis, traced the stages in the lake ecosystem transformation under human impact, laid the foundations for geoecological monitoring using subfossil diatom assemblages. Current research on diatoms in Ladoga sediments focuses on the following: 1) obtaining new data and updating existing ideas about the main stages in the evolution of Lake Ladoga, and revealing bioindication signals of Ladoga ecosystem changes in the geological past; 2) continuing the series of monitoring observations of changes in the composition of surface-sediment diatom assemblages to assess the present state of Lake Ladoga; 3) studying the Ladoga sediments in small-lake basins in the Ladoga region using a modified isolation-basin approach to reconstruct the spatial and temporal frames of transgressive stages of Lake Ladoga.