It's a large tree, populated by lots of very small cats who live in it.

The tree was grown procedurally in voxels using a space colonization algorithm, then rendered to a triangle mesh.

It printed on a Bambu P1S with 0.4mm nozzle, the 0.20 Strength profile, and Bambu PLA filament with no supports. It took over 12 hours to print.

The cats are a "Cute Low Poly Cat (No Supports)" model from https://www.printables.com/model/594620-cute-low-poly-cat by Matthias L ( https://www.printables.com/@MatthiasL ).
The cat model is used under Creative Commons (4.0 International License) Attribution-NonCommercial terms.
The model was not changed other than scaling/translation to incorporate into the tree.
This project is not endorsed by the creator of the cat model and no warranties are provided.
Any sharing of this project must follow the license terms for the cat model.