Multi cellular organisms have 5 different levels of organisation
1. cells - these are the basic structure of function in living organisms basically these are the building blocks of a living organism examples are red blood cells, white blood cells
2.tissues- these are made up of cells that are similar in structure and function in which work together to perform a specific activity examples are muscle tissues, nerve tissues
3.organs- made up of tissues which work together to perform a specific activity examples are heart, brain, lungs etc.
4. organ systems - groups of two or more tissues working together to perform a specific activity or function for the organism. examples are nervous system, circulatory system etc. 
5. organisms - entire living organism that can carry out all basic life processes like growing, reproducing, responding to the nature examples are any living organism like human, flower
hope that helped ;-)
Basic level is cell,, cells grouped together to form tissue.. tissue grouped together to form organ.. organ grouped together to form organ system.. everything together to form organism..
kidney cell -------------- kidney tissue --------------- kidney----------- kidney system ------ animal.