Nucleotides are the building blocks of nucleic acids, like DNA and RNA. They are made up of three main components:

1. A nitrogenous base: This is a molecule containing nitrogen, and it's the part that gives each nucleotide its unique identity. There are five main nitrogenous bases:

* Adenine (A) and Guanine (G) are purines (double-ringed structures)

* Cytosine (C), Thymine (T) (found in DNA), and Uracil (U) (found in RNA) are pyrimidines (single-ringed structures)

2. A five-carbon sugar: This sugar is either ribose (in RNA) or deoxyribose (in DNA). The difference lies in the presence or absence of an oxygen atom on the second carbon of the sugar.

3. A phosphate group: This is a negatively charged group containing phosphorus. It's attached to the sugar molecule and provides the nucleotide with its acidic properties.

Putting it together:

The nitrogenous base is attached to the sugar, and the phosphate group is attached to the sugar as well. This forms a single nucleotide unit.

Here's a simple way to remember:

* Nitrogenous base

* Sugar

* Phosphate

These three components combine to create a single nucleotide. Many nucleotides linked together form a long chain called a nucleic acid.