Breadcrumb User tools Cell organelles Every cell in your body contains organelles (structures that have specific functions). Just like organs in the body, each organelle contributes in its own way to helping the cell function well as a whole. The nucleus , mitochondria and chloroplasts are all organelles. Despite their central importance to cell function (and therefore to all life), organelles have only been studied closely following the invention of the transmission electron microscope , which allowed them to be seen in detail for the first time. Core organelles Core organelles are found in virtually all eukaryotic cells. They carry out essential functions that are necessary for the survival of cells -- harvesting energy, making new proteins, getting rid of waste and so on. Core organelles include the nucleus, mitochondria, endoplasmic reticulum and several others. The primary cilium (which has recently been shown to help cells sense their surroundings) may also be a core organelle because it seems to be present on most cells. Different types of cells have different amounts of some organelles. For instance, cells that use a lot of energy tend to contain large numbers of mitochondria (the organelle responsible for harvesting energy from food). That's why very active muscle cells are often full of mitochondria. Specialised organelles Some cell types have their own specialised organelles that carry out functions that aren't required by all cells. Here are just a few of the specialised organelles that we know about: Chloroplasts are found in plant cells and other