Allah says in another ayat:
يَا أَيُّهَا النَّاسُ ضُرِبَ مَثَلٌ فَاسْتَمِعُوا لَهُ ۚ إِنَّ الَّذِينَ تَدْعُونَ مِن دُونِ اللَّهِ لَن يَخْلُقُوا ذُبَابًا وَلَوِ اجْتَمَعُوا لَهُ ۖ وَإِن يَسْلُبْهُمُ الذُّبَابُ شَيْئًا لَّا يَسْتَنقِذُوهُ مِنْهُ ۚ ضَعُفَ الطَّالِبُ وَالْمَطْلُوبُ – 22:73
“O people, an example is presented, so listen to it. Indeed, those you invoke besides Allah will never create [as much as] a fly, even if they gathered together for that purpose. And if the fly should steal away from them a [tiny] thing, they could not recover it from him. Weak are the pursuer and pursued.”
So He is saying that the disbelievers idols cannot create even something as small as a fly. Similar in this ayat you mentioned Allah is saying we can even look at something as small as a gnat and how Allah has created it with life and all the necessary parts it needs. This is one interpretation.
We do not have to go look at something very large as an elephant to see the complexity in Allah creations we can see the complexity in something very small like a gnat and this makes us say Subhanallah.