Transparent exopolymer particles (TEP) are abundant and significant in aquatic environments, playing a key role in biogeochemical cycles and food web structures. TEP are sticky, gel-like particles composed mainly of acidic polysaccharides. They are formed abiotically from dissolved precursors released by phytoplankton, or through the sloughing of cell surface mucus and disintegration of colonial matrices. TEP can be quantified microscopically or colorimetrically, with results showing consistency between methods. TEP abundances are comparable to phytoplankton, peaking during blooms. As particles, TEP provide surfaces for bacterial colonization and transfer trace substances into the particulate pool. As dissolved polymers, they mix with water and are not filtered or aggregated. TEP enhance aggregation of non-sticky particles, contributing to sedimentation and carbon flux into deep water. Their high C:N ratios suggest they may sequester carbon selectively. TEP turnover ranges from hours to months, depending on chemical composition and age. TEP are also grazed by euphausiids, linking microbial and classical food webs. TEP contribute significantly to carbon cycling and particle dynamics, with their role in aggregation and sedimentation being crucial. TEP are found in various aquatic environments, with high concentrations in coastal areas and during phytoplankton blooms. Their properties, including stickiness and size distribution, influence their role in aquatic systems. TEP formation involves both abiotic and biotic processes, with abiotic formation being significant in some environments. TEP are important for understanding marine biogeochemical cycles and food web dynamics.Transparent exopolymer particles (TEP) are abundant and significant in aquatic environments, playing a key role in biogeochemical cycles and food web structures. TEP are sticky, gel-like particles composed mainly of acidic polysaccharides. They are formed abiotically from dissolved precursors released by phytoplankton, or through the sloughing of cell surface mucus and disintegration of colonial matrices. TEP can be quantified microscopically or colorimetrically, with results showing consistency between methods. TEP abundances are comparable to phytoplankton, peaking during blooms. As particles, TEP provide surfaces for bacterial colonization and transfer trace substances into the particulate pool. As dissolved polymers, they mix with water and are not filtered or aggregated. TEP enhance aggregation of non-sticky particles, contributing to sedimentation and carbon flux into deep water. Their high C:N ratios suggest they may sequester carbon selectively. TEP turnover ranges from hours to months, depending on chemical composition and age. TEP are also grazed by euphausiids, linking microbial and classical food webs. TEP contribute significantly to carbon cycling and particle dynamics, with their role in aggregation and sedimentation being crucial. TEP are found in various aquatic environments, with high concentrations in coastal areas and during phytoplankton blooms. Their properties, including stickiness and size distribution, influence their role in aquatic systems. TEP formation involves both abiotic and biotic processes, with abiotic formation being significant in some environments. TEP are important for understanding marine biogeochemical cycles and food web dynamics.