All living things are made from cells. There are many kinds of cells; some are free to move around from place to place, and others are locked into the tissues of a larger organism. All cells are self-contained little packages, that hold all the tools necessary for survival.
Cells can be of many forms, and can do many different jobs. Some are designed to provide support and protection for the organism they are part of; others process information, carry molecules of food or oxygen, or perform some other useful function.
Cells range in size from the tiny pneumonia cell, one hundred thousandth of a centimetre across, to the yolk of an ostrich egg, which is the size of an orange.
Let's look at what is inside a typical cell. Pictured below is a liver cell.
Like all cells, it has three basic parts:
The nucleus contains genetic information in a material called chromatin. This information is used to direct the cell in its various jobs; it also stores data about the entire organism of which the cell is a part.
The organelles are the tiny organisms inside the cell that perform various jobs.
Here is some more information about the various organelles:
Another organelle, which can be found in plant cells, is the chloroplast. The chloroplast uses energy from sunshine to manufacture food for the cell.