The structure, stability, wetting, spreading, and adhesion behavior of suspensions of nanometer-sized particles depend highly on the many-body interaction forces between the particles and between the particles and the confining geometry. Such is especially the case in concentrated colloidal dispersions when particles are more likely to come in close contact with one another and are confined, where their structural properties are strongly modified in comparison to their bulk properties. The last decade has seen an intensified interest in understanding the role of many-body interactions, which result in attractive depletion and structural forces in fluid-particle systems. This perspective highlights the role of such forces in current and emerging technologies. (c) 2005 Elsevier B.V. All rights reserved.