Dark matter plays an important role in the formation of galaxies.

In our braneworld, about 95 percent of matter is invisible. Its existence was inferred from gravitational effects on visible matter. The invisible matter can be divided into two categories: dark energy (~ 70%) and dark matter (~25%). The dark energy causes the braneword's expansion to accelerate. The dark matter affects stellar motion.

There are three types of dark matter: baryonic dark matter, hot dark matter and cold dark matter. The baryonic dark matter is made up of protons and neutrons such as non-luminous gas and stars. The hot dark matter consists of particles with negligible mass such as neutrinos. Both of them are ordinary matter. The majority of dark matter, however, is the cold dark matter whose physical nature is still not clear. The term "dark matter" often refers to the cold dark matter..

The cold dark matter is made up of heavy particles, about 100-1000 times heavier than a hydrogen atom.  These particles cannot be detected by all kinds of telescopes - radio, infrared, optical, ultraviolet, or x-ray. This means that they do not interact with electromagnetic waves. From their gravitational effects on stellar motion, astronomers have been able to determine their distribution in our space (picture). They are concentrated around galaxies. Computer simulation suggests that the cold dark matter plays an important role in the evolution of our braneworld after the Big Bang - serving as the seed for the growth of galaxies.

Scientists are actively investigating the nature of the dark matter particles. The most likely candidate is the lightest superpartner (LSP) such as the lightest neutralino. Most superpartners of ordinary particles are not stable. They will decay into lighter particles: ordinary particles or another superpartner. It is important to note that a superpartner cannot decay entirely into ordinary particles. At least one of its decay products must be a superpartner. LSP is a stable superpartner because there is no lighter superpartner to decay to. Its mass is about the same as the mass of dark matter particles. The recently constructed Large Hadron Collider (LHC) may provide further information about the superpartners and dark matter particles.

A possible scenario for the creation of ordinary particles during the Big Bang is now emerging. The bombardment of the bulk inflaton with our brane may produce a superpartner (denoted by Pre-LSP) which is the precursor of LSP. The Pre-LSP then decays into LSP and ordinary particles.