Nucleotides are a big deal

This is probably a good place to start looking at the nucleotide. The nucleotide is the building block of all life. It's a complex molecule. It's a major step up in complexity from what lies around it.
Nucleotides distinguish between life (as in atoms, electrons, energy etc.) and living things as in plants animals bacteria etc.
Without nucleotides there would be just a universe of fire and rocks. The step up is hard to visualise but it is like putting a stone into a fire and coming out with something living
You have to ask - how did that happen?
Nucleotides are really complex. They are derived from the elements around them but they are organised in a really complex way with sugar rings and protein chains and things called bases that can pair with complementary bases on other nucleotides. Nothing even comes close to them in the rest of the molecules we have discovered in space. It's like walking through a forest and coming across a shopping centre (sorry it's the best I can do to communicate this). The next bit is even more difficult. Nucleotides have to make themselves. They don't arise in nature spontaneously (and that's because they're so complex) and so they have to make the machinery to make themselves. These properties of nucleotides (they don't arise spontaneously and they need other nucleotides to make themselves) that underlie the properties of what we call living things.