Cells are the smallest unit of life and the building blocks for all organisms. Each component ... what they're made up of. Meat is composed of animal cells, the cell membrane, the cytoplasm ...

And the organism itself. Cells are the building blocks of life. Tissue is made when specialised cells with the same function group together. For example, millions of muscle cells make up muscle ...

They may represent previously free-living organisms that became parasites ... These mobile genetic elements make up an astonishing 42% of the human genome (Lander et al. 2001) and can move ...