Multicellular organism

Multicellular organisms are those organisms containing more than one cell,
and having differentiated cells that perform specialised functions. Although
some single-celled organisms have differentiated cells (e.g. myxobacteria),
the differentiation is less dramatic than that typically found in
multicellular organisms. Multicellular organisms must solve the problem of
regenerating the whole from germ cells (i.e. sperm and egg cells), an issue
that is researched in developmental biology. The overall spatial
organization of differentiated cells is studied as anatomy.

Multicellular organisms can suffer from cancer which occurs when one of its
cells fails to regulate its growth within the normal program of development.