The smallest item in the list would be organelles. Organelles are tiny structures within a cell, that help it to function. Example of organelles are-- nucleus, mitochondria, cell membrane to name a few. Cells are the basic unit of structure and function of all living things, therefore, cells would have to be placed second. They are microscopic. A group of similar cells that work together to perform a specific function, is known as a tissue. Therefore, tissue is next largest. Examples of tissues include, muscle tissue, epithelial tissue, adipose tissue. When different types of tissues work together to perform a function in the body, this group of tissues forms an organ. An example of an organ is the heart. Inside the heart are many types of tissue-- cardiac muscle,nerve, blood, connective, etc. The job it performs is to pump blood. When various organs work together to perform a specific function in the body, this makes up a system. An example is the circulatory system. In this system are many organs that work together. Arteries, veins, capillaries and heart are all part of the circulatory system. Its job is to circulate blood containing nutrients and oxygen to cells and to pick up cellular wastes. All the systems of the body comprise the organism. An organism is a living thing. It can be as tiny as a microbe, or a complex as a human. When referring to a multicellular organism, the correct order from smallest to largest is-- organelle, cell, tissue, organ, system, organism.