Cell: The smallest unit of a living organism is the cell.
A flexible covering known as a cell membrane surrounds all cells, including plant cells.
The cell membrane separates the contents of the cell from the surrounding environment and also controls which molecules can pass through.
Living cells and organelles are all colorless.
When cells are studied under a microscope, they are stained with the appropriate dyes, which causes the cell membrane and other cell organelles to take on the color of the dye.
