What are emergent properties?

Multicellular organisms show emergent properties; these are properties that exist due to many different components working together. For example, your lungs work and help you breathe due to all of the cells in them functioning as a unit; the cells by themselves do not aid you breathing. 

Another way to remember it is "the whole is greater than the sum of its parts"

Even the term "multicellular organisms" can help explain this - they are made up of many cells.

Cells form tissues > tissues form organs > organs form organ systems > organs form multicellular organisms.