Nanocolloids in three Chinese soils were studied with the aid of atomic force microscopy (AFM), and their mean diameter and polydispersity index (PI) were used as parameter to characterize their particle size and morphology. Nanocolloids of JH-4 soil (from Jiuhua, Jiangsu Province) are mainly composed of clay mineral particles of regular sharp, with a mean diameter of 21.5 nm (n=98) and PI of 1.9. The particles are partially coated with colloidal organic matter. Similarly, nanocolloids of FY-1 soil (from Fuyang, Zhejiang Province) have a mean diameter of 20.3 nm (n=133) and a PI of 2.0 though they are irregular in shape and almost completely coated with colloidal organic matter. In contrast, nanocolloids of DX-9 soil (from Dexin, Jiangxi Province) are much larger in mean diameter being 56.3 nm (n=147), but lower in PI being 1.3, spherical and rod in shape, and less coated by colloidal organic matter. Nanocolloidal morphology varies significantly with pH: declining pH coagulates nanocolloids whereas rising pH disperses them. Adding Cu²⁺ to the nanocolloids also coagulates them. These morphological changes may be related to such properties of the nanocolloids as electrical charge and organic matter content. Knowledge on size and shape of nanocolloids and effects of pH and heavy metal ions on them may help understand the roles of nanocolloids in facilitating movement and transport of metal contaminants in soil and water environment.