Interface and colloid science is an interdisciplinary intersection of branches of chemistry, physics, nanoscience and other fields dealing with colloids, heterogeneous multiphase systems that contain extensive interface. One of the examples is colloid solution, which is a heterogeneous mixture in which the particle size of the substance is intermediate between a true solution and a suspension, i.e. between 1–1000 nm. Smoke from a fire is an example of a colloidal system in which tiny particles of solid float in air. Just like true solutions, colloidal particles are small and cannot be seen by the naked eye. They easily pass through filter paper. But colloidal particles are big enough to be blocked by parchment paper or animal membrane. Wetted porous materials, thin oil films on water interface are other examples of systems studied by interfaces and colloid science.
Interface and colloid science has applications and ramifications in the chemical industry, pharmaceuticals, biotechnology, ceramics, minerals, nanotechnology, and microfluidics, among others.