The first thing God created was what we now call space. The collective name in Hebrew is Ha Shamayim, as in the heading. Dual in form, for the single form Shamah never being used, is apparently from an old root meaning "to be aloft". However, God names the so-called expanse by this name, so it is to 1:9 that one must go for a definition.
Working from the specific to the general, and taking the name as synonymous with the thing named, the expanse (רָקִיעַ), that is stretched out fabric of space is the same as heaven, or the heavens.
Usage determines the translation of שָּׁמַ֖יִם. Often it is localized, sometimes it is global, but most often the space occupied by heavenly and spiritual beings.
The ancient readers may have expected a tiny unseen world smaller than dust, but the Bible does not reveal anything along those lines. However, they understood that the heavens extended far above the mountaintops.
The loftiness of heaven helps to magnify its creator. The magnitudes of size extends from the dust of the ground to the vast galaxies
We know today that a vast tiny world lives in among the aforementioned dust, aka dirt. Those unseen creatures are made up of molecules there is so much space that explorers can only imagine the space inside of the nucleus.
It is to that smallest pocket of inner space that we will go next.