She smiled, looking a little sheepish, but it was probably obvious that this wasn't the first time that she had been told something similar about her definition of neat or fun.
"Well... they're what DNA and RNA have and basically make up all of life. At least on Earth. Without it, we wouldn't be who we are." She pointed to the DNA strand example on the page of his book. "See how these two strands of DNA look almost the same? That's because one of them is child of the first."