Cells are one of the most important things on Earth today, and have been one of the most important things on Earth for a very long time. Without cells, to put it simply, organisms just would not exist at all. In any living organism, cells are the things that allow every minute function, and as such are extremely important. Although many people know that cells are the building blocks of life, they do not know what a cell does, how it functions, or even what the purpose of that cell is.
As cells are one of the most basic units in life, no one could live without them. In unicellular organisms, the cell literally is the organism, that is one cell carrying out all the functions needed for that organism. In multicellular organisms, things get a bit more complicated, cells are diversified into separate roles that allow them to carry out these functions. These cells then work together with one another to complete tasks within the body, this is called tissues. These tissues then combine with one another to carry out a specific function, and the tissues become organs. When multiple organs are working to do the same thing within a body, these organs become an organ system within it. Finally, an actual organism functions with all of these organ systems functioning to make that organism work right.
Cells may be the building of blocks of life, but all cells are made up of even smaller parts called organelles. These organelles, like organ systems all serve specific functions throughout the cell. Within the cell are many different types of these organelles, the most common organelles in animal cells are, the cell membrane, the ribosomes, the lysosomes, the endoplasmic reticulum, the golgi apparatus, the mitochondria, the nucleus, and the cytoplasm. The cell membrane is a simple enough organelle, its basic purpose is to keep the contents of the cell held in and keep harmful things, like a virus, out of the cell. Ribosomes are the protein producers of the cell, making protein so the cell can continue to function. The lysosomes are much like the waste management of the cell, they recycle unusable parts of the cell. The endoplasmic reticulum takes in proteins made in ribosomes, and serves much like a transportation system. The golgi apparatus takes the proteins delivered by the endoplasmic reticulum, and processes them so they are ready for use. The mitochondria serve as the powerhouse of the cell, where energy for the cell is produced. The nucleus could be considered the control center of a cell, and contains the DNA of the cell. Finally the cytoplasm is the watery content within a cell in which all the organelles reside.
All of these things can attest to how powerful and complex a cell really is, but what is the purpose of these cells? The short answer is the purpose of these cells is to keep one alive, or even in existence. There are roughly ten trillion cells in a normal adult human body, each of them being diversified to serve a specific purpose. Millions of these cells die off each day, but are replaced when the cells divide in a complex process. Without this constant influx of cells, none of the human organs, or organ systems would be able to function, and all life as anyone knows it would be completely gone. Due to this, cells serve a highly regarded and important purpose, they literally keep all living things in existence.