Looking at moss, pond water, microbes, tardigrades, paramecia, cells, plants, crystals, stuff around the house

You can get a decent microscope for like $250 and just get a smartphone mount to take high quality pictures/videos.

I feel like with astronomy/telescopes you spend a ton of money just to see a blurry blob whereas microscopes are way more bang-for-buck in terms of how much cool science stuff you can see for cheap.