interesting
Most unicellular organisms are of microscopic size and are thus classified as microorganisms.
However, some unicellular protists and bacteria are macroscopic and visible to the naked eye.
Examples include:
Xenophyophores are the largest examples known, at roughly 4 inches.
Valonia ventricosa, with a diameter of 1 to 4 centimeters it is one of the largest single-celled organisms.(see pic)
Syringammina fragilissima
Thiomargarita namibiensis