The unit of life is the "cell".
A cell is the basic unit of life, the smallest and simplest living component of all living organisms. All organisms, including plants, animals, and bacteria, are made up of one or more cells.
A cell performs all the essential functions of life, such as metabolism, growth, reproduction, and response to stimuli. Within a cell, there are different structures and organelles that carry out specific functions to keep the cell alive and functioning properly.
Tissues, organs, and systems are made up of multiple cells working together in a coordinated manner to perform more complex functions, but the cell is the fundamental building block of life.