The article discusses the significant role of dissolved organic matter (DOM) in the global carbon cycle, particularly in the ocean. Initially, DOM was thought to be a spatially invariant, biologically refractory pool of carbon, but early studies by Sugimura and Suzuki in 1988 challenged this view by reporting much higher concentrations of dissolved organic carbon (DOC) and nitrogen (DON) than previously accepted values. This sparked a controversy that led to extensive research efforts to validate these findings. Despite initial skepticism, improvements in analytical techniques and global ocean hydrographic surveys have provided new insights into the dynamics and variability of DOM. DOM is a major reservoir of reduced carbon in the ocean, with concentrations ranging from 34 to 80 μmol kg\(^{-1}\) in the open ocean. The biological pump, which transports biogenic carbon from the surface to the deep ocean, plays a crucial role in sequestering carbon. DOC contributes significantly to this process, especially in regions with strong vertical gradients and active overturning circulation. High-precision measurements and global data sets have revealed that semi-labile DOC, which has a shorter turnover time, is more reactive and contributes to the biological pump, while refractory DOC, which has a longer residence time, is more resistant to microbial degradation. The article also highlights the importance of abiotic processes, such as photolysis and particle interaction, in the removal of refractory DOC. These processes can lead to the formation of particles that sink through the water column, contributing to the deep ocean's carbon sink. The study emphasizes the need for further research to understand the molecular composition of DOM and develop tracers for nonadvective additions of DOM to the deep ocean. Overall, the renewed focus on DOM has led to significant advancements in our understanding of the ocean's carbon cycle, challenging traditional paradigms and opening new avenues for future research.The article discusses the significant role of dissolved organic matter (DOM) in the global carbon cycle, particularly in the ocean. Initially, DOM was thought to be a spatially invariant, biologically refractory pool of carbon, but early studies by Sugimura and Suzuki in 1988 challenged this view by reporting much higher concentrations of dissolved organic carbon (DOC) and nitrogen (DON) than previously accepted values. This sparked a controversy that led to extensive research efforts to validate these findings. Despite initial skepticism, improvements in analytical techniques and global ocean hydrographic surveys have provided new insights into the dynamics and variability of DOM. DOM is a major reservoir of reduced carbon in the ocean, with concentrations ranging from 34 to 80 μmol kg\(^{-1}\) in the open ocean. The biological pump, which transports biogenic carbon from the surface to the deep ocean, plays a crucial role in sequestering carbon. DOC contributes significantly to this process, especially in regions with strong vertical gradients and active overturning circulation. High-precision measurements and global data sets have revealed that semi-labile DOC, which has a shorter turnover time, is more reactive and contributes to the biological pump, while refractory DOC, which has a longer residence time, is more resistant to microbial degradation. The article also highlights the importance of abiotic processes, such as photolysis and particle interaction, in the removal of refractory DOC. These processes can lead to the formation of particles that sink through the water column, contributing to the deep ocean's carbon sink. The study emphasizes the need for further research to understand the molecular composition of DOM and develop tracers for nonadvective additions of DOM to the deep ocean. Overall, the renewed focus on DOM has led to significant advancements in our understanding of the ocean's carbon cycle, challenging traditional paradigms and opening new avenues for future research.