Verified Answer :

sgttrumbo

Tissues. 
When large groups of tissues form up, they create tissues which the body will use to form organs.
Here is the cell levels in order for future reference:
Cells - Tissues - Organs - Organ Systems - Organisms

taskmasters

The basic
unit of a living organism is a cell. Cells with the same function and structure
comprises to makes up a tissue. A group of tissues combined with similar
structure and forms makes up an organ. A group of organs with relative function
makes up a system. Lastly, a group of system with relative functions make up an
organism. To simplify:

Cell-->
Tissue--> Organ--> System --> Living Organism.