Left and right hemispheres of the brain of Rajat Jain (25) obtained with an MRI scan and used in UCSF's and UCSD's glassbrain project. I got the 3d files from the National Institutes of Health 3D Print Exchange web site.

There are two STL files, which came from these respective URLs:
Left Side: https://3dprint.nih.gov/discover/3DPX-000757
Right Side: https://3dprint.nih.gov/discover/3DPX-000758

Print instructions

The GCODE prints both hemispheres at the same time. Note that the model contains internal brain structures that cannot be seen on the print, so I chose to use the PrusaSlicer Support All option to fill any internal voids.

The two sides fit together nicely, as you can see in one of the photos.