If you scoop a glass of water from the sea and look beyond the wonders of biology therein, you see particles (Fig.l). Detritus of the many biogeochemical processes at work in the ocean, particles influence fundamentally the transport of mass and transmission of energy through the water column. Particle sinking is a major pathway for transfer of carbon and nutrients from surface waters to the deep sea, thereby playing a crucial role in global climate (Suess, 1980; Asper et al., 1992). Particles offer abundant surface area for adsorption of numerous hydrophobic anthropogenic contaminants, so the fate of pollutants in the sea is linked inextricably with the fate of particles (Milligan and Loring, 1997; Gustafsson et al., 1998). Particles scatter light, so they affect the growing conditions for phytoplankton at the base of the oceans’ food webs (Campbell and Spinrad, 1987; Bricaud et al., 1995). Concealed within particles that come to rest on the seafloor is a record of environmental change that paleoceanographers and geologists are devoting great effort to unraveling (Kranck, 1984; McCave et al., 1995). The list of particle roles in the sea goes on, but perhaps this one is sufficient to make the point that understanding of particles is a keystone for overall understanding of the seas.