Abstract <p>The review presents the key results on investigation of biosilica produced from diatoms and its application in various fields of science and technology. The review aims at systematic presentation of the data on the properties, modification techniques, and areas of application for this material. The data on the properties of biological silica are generalized; the main methods for modification are discussed, which result in a significantly broadened spectrum of the functional characteristics of this material. Special attention is paid to the application of nonmodified and modified biosilica in biomedicine as drug nanocarriers, materials for tissue regeneration, treatment of infected wounds, as well as biosensors and matrices for SERS analysis. The data are presented on its efficiency for environmental applications, including removal of heavy metals, organic dyes, and solvents from wastewater. New promising applications of biosilica, including its use in energetics, chromatographic analyses, and other innovation areas, are discussed separately. The review summarized up-to-date information and stresses the significance of development of new modification techniques to broaden the functional abilities of this unique material.</p>