Multicellular Organism

Multicellular organisms are organisms that consist of more than one cell. Each cell is specialized to do a certain job for that organism. Most life that can be seen with the naked eye is multicellular, as are all members of the kingdoms Plantae and Animalia (except for specialized organisms such as Myxozoa). Read more 

Types of multicellular organism

1. Mutlicellular prokaryote: Most bacteria are unicellular, but some bacterial species are multicellular like Myxobacteria. Some species of cyanobacteria are also multicellular like Chara, Spirogyra etc. Magnetotactic bacteria are also multicellular. But some biologists consider these organisms as "colonial", instead of multicellular.
2. Multicellular eukaryote: Most eukaryotic organism are multicellular. Multicellular organisms have well developed body structure and also have specific organs for specific function. Most well developed plants and animals are multicellular. For example almost all species of gymnosperm and angiosperm are multicellular in plants. All animals are eukaryotic in nature and most of them are multicellular.