There are single-cell organisms up to an inch or so in diameter. https://en.m.wikipedia.org/wiki/Valonia_ventricosa https://en.m.wikipedia.org/wiki/Valonia_vent

There are single-cell organisms up to an inch or so in diameter. https://en.m.wikipedia.org/wiki/Valonia_ventricosa https://en.m.wikipedia.org/wiki/Valonia_ventricosa There are even visible bacteria! https://www.science.org/content/article/largest-bacterium-ever-discovered-has-unexpectedly-complex-cells https://www.science.org/content/article/largest-bacterium-ev...