A plant cell wall is made of cellulose, which is a complex sugar. The cell walls both protect and provide shape and structure for plants' cells, allowing some to reach great heights.
Only plants have cellulose cell walls, but some other organisms have cell walls made of different materials. Plant cell walls vary in flexibility and thickness. Small plants have slightly elastic cell walls, which allow them to flex and then regain their shape. Larger plants, like the tallest trees, have thick and strong cell walls that resist large forces. Regardless of their thickness, all plant cell walls have holes to allow materials to pass between cells.