You have probably heard that humans are made up of mostly water. So, why don't we collapse into puddles on the ground? That is because the human body is made up of all different types of cells – skin cells (which are really flat), heart cells (which beat – for real!), and brain cells (which transmit information), to name a few. Cells have an important feature that prevents us from collapsing into puddles on the ground: they have an outer membrane, made up of special fat molecules, that keeps the water inside from leaking out! Inside the cells, there are more fatty membrane compartments called "organelles" that all have their own important jobs. One of the most important organelles is the nucleus. This is where the genetic information in the form of deoxyribonucleic acid (DNA) is found. The nucleus controls which different proteins are expressed in each different type of cell. The proteins are the busy workers in the cell because they perform important jobs to allow the cell to do what it needs to do!

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Go to source: https://kids.frontiersin.org/article/10.3389/frym.2016.00020