Cells were not "invented" in the way that a machine or tool is invented. They are the fundamental building blocks of all living organisms, and their existence predates any human activity.

Here's a breakdown:

* Cells are the basic unit of life: All living things, from the smallest bacteria to the largest whales, are made up of cells.

* Cells existed long before humans: Life on Earth has existed for billions of years, far before humans evolved.

* Discovery, not invention: Cells were not invented, but discovered through scientific observation.

* Robert Hooke's observations: In 1665, Robert Hooke was the first to use a microscope to observe and describe cells, although he was looking at the cell walls of cork, not living cells.

* Antonie van Leeuwenhoek: Later, in the 1670s, Antonie van Leeuwenhoek used more powerful microscopes to observe living cells in pond water and other samples.

So, while we can pinpoint the discovery of cells through scientific observation, their existence is as old as life itself.