Robert Brown didn't actually describe a cell as we understand it today. He was the first to observe and name the cell nucleus in 1831. He was studying the structure of orchid cells under a microscope and noticed a small, opaque spot within each cell. He called this spot the "nucleus" because of its central location within the cell.

It was Matthias Schleiden and Theodor Schwann who later developed the cell theory in the 1830s. They proposed that all living organisms are made up of cells, and that cells are the basic units of life.

So, while Brown didn't describe a cell in its entirety, his discovery of the nucleus was a crucial step in understanding the structure and function of cells.