According to the big bang hypothesis, the all of the current present and past matters came into existence nearly 14 billion years ago. At this time all the matter was compacted into a very small ball with intense density and intense heat called a singularity. It is accepted fact the universe started to took its form when this singularity started to expand and its still expanding at speed of 82.4 kilometers per second permegaparsec.
This led to creation of planets stars and the other celestial bodies. In the beginning the temperature was not adequate to support any sort of life. Soon after the explosion the temperature started to decrease rapidly to1 billion kelvin within seconds. And it continued for billions of years. After attaining the stability , planets and other started gaining their present states.
There are two theories which rose due to big bang expansion. Contraction and slowing down of expansion known as big freeze. In the first scenario known as big crunch .the universe will reach maximum of its size and then will start collapsing. In the second scenario, the universe may never stop expanding but may slow down. In this scenario all existing stars will burn out into white dwarfs , neutron stars and black holes. Thus their collisions will increase forming larger black holes. The temperature universe would approach to zero and black holes will evaporate after emitting the last of their hawking radition.