half.fast said:

If you look at [plant] cross sections of these structures under a microscope you'll find that the cells have differentiated into many different types, making it easy to tell what you're looking at without any help. Roots look like roots, stems look like stems, leaves look like leaves, etc.

Basidomycetes (our mushroom producing fungal friends), can grow below the surface (in soil, or wood, etc.) or, when mushrooms are produced, above ground, too. If you take some of the bits growing below the surface and compare them microscopically to the bits growing above the surface as a mushroom, do you know what you'll see? You'll see exactly the same thing

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