(I'm astrophysicist Neil deGrasse Tyson.) Some with billions, others with trilions of stars, these are the fundamental building blocks of visble matter in the universe; they come in many varieties including spiral, irregular & elliptical
In 
reality, these are two galaxies 400 million light-years away from Earth in the ...... 
small region of a galaxy the building blocks of a star are blown out by a dying star
.