What type of cells are recognized as the smallest units of life?

Cells are recognized as the smallest units of life because they are the fundamental building blocks of all living organisms. Each cell acts as an independent unit capable of carrying out necessary life processes, including metabolism, energy conversion, and reproduction. Regardless of their specific type—be it neurons, muscle cells, or blood cells—each of these is a specialized form of cell that contributes to the overall function of an organism but does not stand alone as the basic unit of life. Thus, the broad classification of "cells" encompasses all living forms, from unicellular organisms to complex multicellular organisms, highlighting that cells, in general, are the smallest units that exhibit all the characteristics of life.