The title of "biggest living cell" is a bit tricky, as it depends on how you define "biggest."

Here are two contenders:

* The Giant Amoeba: This single-celled organism can reach sizes of up to 5 mm, making it visible to the naked eye. These amoebas are found in freshwater environments and are known for their ability to change shape and engulf food.

* The Ostrich Egg: While not strictly a single cell, the ostrich egg's yolk is technically one giant cell, containing all the nutrients needed for the developing embryo. It can reach a size of 15 cm in diameter and weigh up to 1.5 kg.

So, while the Giant Amoeba might be the largest single-celled organism by size, the Ostrich Egg's yolk is the largest individual cell by volume.

There are other contenders for "biggest" depending on the criteria used. For example, some types of algae can form large, multicellular colonies.