Here's why:
* Tissues are collections of similar cells that work together to perform a specific function.
* Organs are made up of different tissues working together for a larger purpose.
* Organ systems are groups of organs that work together.
So, you could think of it like this:
* Cells are the building blocks.
* Tissues are like the bricks.
* Organs are like the rooms built with the bricks.
* Organ systems are like the whole house made up of the rooms.
