Cosmos is collection of of all particles and energy that exist. Eventually we are also made-up of Cosmos as we are the part of the big universe. The Early universe which was formed after the instance of Big Bang was a huge area of Star-dust. The Amount of Star-dust inside of our body is impressive.
Any element heavier than hydrogen is ultimately a product of the nuclear fusion that takes place within stars. When big stars die, they tend to explode a lot of heavier elements out into space, which become nebulae. These nebulae often coalesce into new stars and, sometimes, planets. Some of those planets (well, one at least) have people on them, so people are in a sense made of “star-dust”.