How do cells in single-celled and multi-cellular organisms differ?

The main difference between unicellular and multicellular is some organisms are made-up of single cell termed as unicellular while multicellular are made-up of two or more cells. Single celled organism is called unicellular organism ... Unicellular organisms have greater surface area to volume ratio. multicellular is a complex organism, made up of many cells. Humans are multicellular. While single-celled organisms can't usually be seen without a microscope, you can see most multicelluar organisms with the naked eye. single are like bacteria