 Our body is a pretty fantastic piece of engineering, but how does it work? How do all of the different components come together to keep us alive, keep us functioning and achieving our goals? In this video we're going to look at the levels of organization in organisms, from smaller than cells to bigger than organs. In unicellular organism, the single cell performs all life functions. However, multicellular organisms have various levels of organization within them. To learn more about the differences between unicellular and multicellular organisms, watch this video. All living things are made up of cells. This is what distinguishes them as living. Cells are the building blocks of life. Inside cells are little organelles. These are specialized structures that carry out particular jobs or functions. Like in this animal cell, the mitochondria provides energy to the cell and the ribosomes are involved in protein synthesis. Cells themselves are the basic structure that make up living organisms. In multicellular organisms, they are differentiated to carry out different roles. Here are few specialized human cells. Groups of cells then form together to form tissues. In humans we have four main types of tissue. Main plants, the xylem and phylum, are examples of plant tissues. When there are layers of tissue working together, they form an organ. Organs are specialized to carry out specific life processes. All animals contain organs. In fact mammals have five vital organs that they cannot live without. Lungs, kidneys, liver, heart and brain. Like plant-type organs too, these specialized organs work together in organ systems performing body functions. Organ systems keep the body regulated and in stable state. The human body has eleven organ systems. Organisms are entire living things that can carry out all basic life processes. Multicellular organisms are made up of organ systems but unicellular organisms such as bacteria or protists are made up of one cell. So they are the levels of organization in multicellular organisms.