The tutorials I found useful for creating these neurons the way I wanted them:
Neurons:
https://www.youtube.com/watch?v=_NkYxUDNENg&list=PLN5G0IW9nROauqy9Rxrfzn731F5UvjyFZ&index=3
Brain:
https://www.youtube.com/watch?v=27WhXoA1LcQ&list=PLN5G0IW9nROauqy9Rxrfzn731F5UvjyFZ&index=9
Stem cells:
https://www.youtube.com/watch?v=SosbjeH7jeg&list=PLN5G0IW9nROauqy9Rxrfzn731F5UvjyFZ&index=2