In the beginning, the size of the Universe is too small that it can't be seen through human's naked eye. It is like a dot but it contains the strongest force ever identified by Physics. This force is known as Super Unified Force. Because of an unknown imbalance, the super unified force separated to four fundamental forces in just a split of second. This four fundamental forces have different strength. Because of their existence, the Universe that once governed by energy and forces started to have matters and other physical manifestation of energy. The four fundamental forces are the strong nuclear force, weak nuclear force, electromagnetic force, and Gravitational force.
The Gravitational Force
You might asking the reason behind the revolution of the moon around the Earth and the Earth around the Sun. Why is it that galaxies, clusters, and superclusters are existing? Why is it that we are standing on the Earth's surface? This is because of Gravitational force. The force, that is also known as the force of attraction, is existing between and among matters that has mass. The greater the mass an object, the greater its force of attraction. This is the reason why, the Sun is attracting the Earth around it while the Earth is attracting the moon around it. This also allows us to stand on the earth's surface. Gravity are well spread, however, this is the weakest force if compared from the other three forces. This force is contained in a force carrier particle known as Graviton.
Electromagnetic force
Electricity, lightning, light--- those are all existing because of electromagnetic force. This causes the attraction and repulsion between protons (positive charge subatomic particles) and electrons (negative charge fundamental particles). This is contained in a force carrier particle, known us Photon.
Strong nuclear force
Strong nuclear force is the strongest force among the four fundamental forces. It is the one that is connecting quarks together to form protons, and neutrons. Furthermore, it holds protons, and neutrons together to form nucleus of an atom. This is contained in a force carrier particle, known us Gluon. This is the strongest but are bundled in tiny particles and contained within the nucleus of an atom. Why is it that gravity is the force that is connecting planets together, not strong nuclear force. If that is the cases, it will pull all matters together, which could form again a super unified force.
Weak nuclear force
Weak nuclear force is the second weakest fundamental force, however, don't underestimate it because it might be weak but it is strong enough to contribute in the formation of unstable elements . This is contained in two force carrier particles known as W and Z Bosons. It has an important role in the existence of radioactive or unstable elements that are also the reason why heavier elements than iron or nickel are existing.