Eukaryota is one of the three main domains of life, which includes organisms with complex cells. These cells have a defined nucleus that contains their genetic material, unlike Prokaryota, which are simpler and lack a nucleus. Eukaryotic organisms can be unicellular, like yeast, or multicellular, such as plants and animals. Eukaryota is further divided into several kingdoms, including Animalia, Plantae, Fungi, and Protista. Each kingdom has unique characteristics and plays a vital role in ecosystems. For example, plants are essential for photosynthesis, while fungi help decompose organic matter, recycling nutrients back into the environment.