Cell biology

Cell biology is the study of how living cells work. This includes the structure and function of the cell organelles, and the carbon-based molecules which cells produce. Cell biology is an interdisciplinary subject, and uses ideas from genetics, biochemistry, molecular biology, immunology, and other subjects and techniques. 
The most important molecules in cell biology are DNA, RNA and proteins.
The most important structures in the cell are the nucleus and the chromosomes, but there are others. The structure of eukaryotic cells is much more complex than prokaryotic cells. This is because endosymbiosis has occurred: some or all of the eukaryote organelles are former prokaryotes. Examples are mitochondria and plastids.
The most important function of cells is to divide by mitosis or meiosis. Cells in a multicellular organism also specialise in different functions, and the different types may look quite to each other.