This article reviews principal mechanisms of soil C sequestration, with a particular reference to soils from Latin America. Four main processes are considered: i) the relationship between SOC and aggregation, ii) the interaction of C with clay fractions, iii) the role of dissolved organic C (DOC), and iv) the formation of secondary carbonates. i) Long chain polymers play an important role in aggregation. There is a range of biotic factors that affect the formation of stable aggregates. Fungi, bacteria, roots and larger soil organisms, like earthworms are key actors in the active regulation of soil structure, and most interact in more than one mechanism of stabilization at different spatial and temporal scales. ii) The relationship between clay type and content and organic matter accumulation and stabilization is complex. Clay minerals exhibit different morphologies which determine the different packing characteristics. The interaction of C with clay particles is a primary factor in the stabilization of organic matter (OM) in aggregates, especially in the high-activity swelling clays. iii) The flow of DOC is an important process for the transport of C through soil. The flux of DOC represents an important mechanism by which the distribution and stabilization of C in soils occur, or the control it exerts in the activation of soil microorganisms at certain soil depth. Movement of DOC may occur with clay colloids. iv) Finally, the role of soil inorganic carbon (SIC) is important for sequestering C, but the mechanisms involved are not well understood. The formation of secondary carbonates also occurs in soils of the humid tropics, and the rate of sequestration seems to be low. Leaching of bicarbonates is another mechanism of transport of C into the groundwater. The importance of observation levels and scales in the four processes are also addressed and discussed.