The 8 planets in our Solar System were born from the remnants of our Suns formation. This was a process that lasted over millions of years within vast clouds of gas and dust.

The journey begins with a nebula, a giant cloud of gas and dust. As the nebula collapsed under its own gravity, it began to rotate and flatten out into what's called an accretion disk. With a young star, our Sun, forming at its center. This spinning disk held the building blocks of the future planets.
The contents of the accretion disk is not the same from the center to the outer edges. Closer to the hot, young star, only materials such as different metals and rock can exist in solid form. Further out, in the colder parts of the disk, volatile compounds like water, methane, and ammonia freezes into ice particles.

Within the disk, the process of accretion begins. At first, tiny dust grains start to stick together through electrostatic forces, much like dust bunnies forming under a bed. Over time, these clumps grow larger, forming pebble-sized and then boulder-sized bodies. As these objects become more massive, they begin to develop gravity, allowing them to attract and sweep up more dust and smaller debris in their path around the Sun.

Through continuous collisions and mergers, this debris bodies grow into planetesimals, which can be several miles in diameter. The gravitational pull of the largest planetesimals becomes significant, and as a result, allows them to attract and absorb their smaller neighbors at an accelerated rate.
Eventually, after a few million years, these larger bodies form into protoplanets, which are essentially "baby" planets. The final stage of a planets formation involves the violent collisions of these protoplanets over tens of millions of years.
In the inner, hotter regions of the accretion disk, the rocky protoplanets that formed became the terrestrial planets: Mercury, Venus, Earth, and Mars. In the cold, outer regions, the protoplanets were able to gather not only rock and metal but also huge amounts of the abundant frozen gases. This allowed them to grow into the gas giants (Jupiter and Saturn) and ice giants (Uranus and Neptune) that we see today. The remaining gas and dust in the accretion disk were eventually blown away by the strong stellar winds of the young star.