1. A nitrogenous base: This is a molecule with a nitrogen-containing ring structure. There are five main types: adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U).

2. A five-carbon sugar: This is a sugar molecule with five carbon atoms. The most common types are ribose (found in RNA) and deoxyribose (found in DNA).

3. A phosphate group: This is a molecule containing phosphorus and oxygen atoms.

These three components are linked together in a specific way to form a nucleotide.