Is intelligence made through nutrition, training, nurture, or genes?

I had a dream telling me that if I wanted my future kids to be smart, I should teach them when they are young.

My grandma taught me grade 5 math when I was 4 years old and until high school, I always got 100% in math and it was easier than breathing for me. I trained in math at a young age, so for me, math was easier than breathing.

Is intelligence made through nutrition, training, nurture, or genes?
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