group of cells with similar structure that have a special function.

Merriam-Webster Online Dictionary
tissue (noun)
1.
a) a fine lightweight often sheer fabric
b) - mesh network web a tissue of lies
2.
a piece of soft absorbent tissue paper used especially as a handkerchief or for removing cosmetics
3.
an aggregate of cells usually of a particular kind together with their intercellular substance that form one of the structural materials of a plant or an animal
tissue (Wikipedia)

Tissue may refer to:

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