Groups of cells that work together to do a specific job

Many cells = tissue
Many tissues = organ
Many organs = organ system
Many organ systems = organism

Group of cells = tissue
group of tissues = organ
many organs = organ system
organ system = body/organism
                                       
      Systems

Circulatory System    
Digestive System     
Endocrine System                                
Lymphatic System       
Muscular System     
Nervous System                                
Reproductive System     
Respiratory System     
Skeletal System 
Urinary System     
Integumentary System

They are all solids.