Cells and organisms

• Tissue

  A group of cells with similar structures, working together to perform a shared function.
• Organs

  A structure made up of a group of tissues, working together to perform specific functions. The stomach is an organ.
• Organ system

  A group of organs with related functions, working together to perform body functions. Like, disgestive system, excretory system, etc.
• Cells make up tissues, which make up organs, which make up organ systems, which make up organisms.