Let’s suppose that before inflating the balloon, I write a message on the surface of the balloon which is so tiny that you cannot read it. Inflating the balloon will make the message readable for you. This means that inflation acts as a microscope, which magnifies what was written on the initial balloon.In a similar manner we are able to observe quantum fluctuations that were created at the beginning of inflation. The expansion of the Universe during the inflationary epoch serves as a huge microscope that magnifies quantum fluctuations, corresponding to a scale less than 10-28cm, to cosmological distances. This leaves imprints in the cosmic microwave background radiation (hotter and colder regions) and in the distribution of galaxies.
Inflation works as a cosmic microscope to see the quantum fluctuations in the very early Universe.
Using classical physics, the evolution of the inflationary Universe is homogeneous – each spatial point evolves exactly the same way. However, quantum physics introduces some uncertainty in the initial conditions for the different spatial points.
These variations act as seeds for structure formation. After the inflationary period, when fluctuations are amplified, the density of matter will vary slightly from place to place in the Universe. Gravity will cause the more dense regions to start contracting, leading to the formation of galaxies.