Here's why:

* Single Cell: Amoebas are made up of just one cell.

* Independent Life: This single cell carries out all the functions necessary for life, such as movement, feeding, and reproduction.

* Microscopic: Amoebas are tiny and can only be seen under a microscope.

Other examples of unicellular organisms include:

* Bacteria

* Paramecium

* Euglena

* Yeast