Some of the magic, but for 1/10th the price and extremely portable. I'd recommend getting an objective whether or not you also buy a stereo zoom scope.
These have much, much sharper optics than the clip-on lenses that are commonly sold. It's a whole world of difference, and for cheaper.
After testing several 4X objectives, I'm quite confident that this is the best for phone mounting. The end section is removable and contains no optics, making the working distance even longer (which is great when you don't want to scare off some bug). The field of view is oddly higher than the others, even with the same technical specs, so you'll only need to use ~2X digital zoom to fill the frame on your phone camera, rather than the 4+ on others.
Mounting! I like to 3D print a half-case that fits my phone and aligns the lens, and then screw in one of the RMS to M25 adapters to make lens swapping easy.
3D models, and more fun support files
Why not higher magnification? You can buy 40X or even 100X microscope objectives, but they're incredibly difficult to use. The working distance is often <1mm, so the lens has to be pressed against the subject. Higher magnification also means less light collection, so there's rarely enough ambient light to get a good image. The bit that truly wrecks these is that the in-focus plane is so thin that even your heartbeat moving your hands is enough to completely lose what you were trying to see.