A star comes to the end of its life. It explodes as a supernova,
showering particles out into the space – some light, gaseous, others
heavier, such as soot (carbon) and sand (silica).

Where these particles are swept together at sufficient density, perhaps
around a young star, itself formed from collapsing clouds of hydrogen
and helium eg in the Orion Nebula, they form larger and larger dust
grains. When they reach about a kilometre diameter, then can begin to
congregate gravitationally rather than randomly. From these
planetesimals, larger and larger masses form eg planets, moons (eg
Phobos and Deimos, the moons of Mars), comets, asteroids. From the
starborn atoms of carbon come the building blocks of life – carbon
dioxide in the atmosphere, captured by plants, eaten by animals,
recycled into new life, new tissues, the skin on the tip of your little
finger.