pores

Pores are small openings or spaces within a solid substance or biological tissue that permit passage of gases, liquids, or other substances. They occur in living organisms, soils, rocks, and manufactured materials, and they play a key role in exchange, transport, filtration, and reaction processes. Pores may be open to the exterior or internal, and they may form networks.

In biology, skin pores are openings of hair follicles and sweat ducts; pore size varies and can be influenced by age and hormones. Plants have stomata, pores on the leaf surface that regulate gas exchange and water loss. At the cellular level, nuclear pore complexes regulate transport between the nucleus and cytoplasm.

In geology and soil science, porosity is the fraction of void space in a rock or soil, affecting water and air storage and movement. Pores can be microscopic to macroscopic and may be open (connected) or closed (isolated). In rocks, pore networks control fluid storage and flow; in soils, they influence drainage and root growth.

In materials science, porous materials such as activated carbon, ceramics, metals, and polymers are engineered with specific pore sizes and connectivities to optimize filtration, catalysis, insulation, or diffusion. Porosity and pore connectivity are characterized by size distribution and surface area, guiding applications from filtration to environmental remediation.