Antony van Leeuwenhoek, the inventor of the microscope, is also credited with the discovery of cells (they were cork cells). Cells exist as a self contained way to store/replicate DNA and do a particular function.
Cells are the buildings block of life. Every living creature is made from cells. Cells are the workers of the body and what the body does is a large combination of cells. I think someone named Hook discoverd them.
Of course cells exist. We are made up of billions of cells. All plants , animals, bacteria, fungi, and microorganisms are comprised of cells. They exist all of the time