A tissue is a group of similar cells, bound together, that work as a team on one job. Muscle tissue is built from cells specialised to contract. Nerve tissue is built from cells specialised to carry signals. On their own, a single muscle cell can only shorten by a tiny, unnoticeable amount — but millions of them, organised into a tissue and then into a muscle, can lift real weight. Grouping specialised cells together is what lets the body do things a single cell never could manage alone.