After all, radiowaves, microwaves, and visible light are all electromagnetic radiation; they differ only in frequency. So other things equal, a microwave circuit shrunk down by a factor of 100,000 will behave the same way but at 100,000 times higher frequency.
Since radio waves, microwaves, and visible light are all forms of electromagnetic radiation, their behavior depends on their frequency. A smaller microwave circuit, shrunk by a factor of 100,000, would function similarly but at a much higher frequency.