You´ll find 45 Object each with a certain value parameter set. Adjustable in the Geometry Node setup. The "red" Value Node Boxes are the parameter to generate the shell form. Behind is a combination of different math formulas used to build up the different shells. Of course there are a endless possibilities to generate new, your own shells. 

Behind the Group node are the main formula. If you are curios, you can try to make your own variation.

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