The type of cells that have nuclei and membrane-bound organelles are called eukaryotic cells. These cells are more complex than prokaryotic cells, which lack a defined nucleus. Eukaryotic cells can be found in a wide range of organisms, including plants, animals, fungi, and protozoa. The nucleus houses the cell's genetic material, while the organelles, such as mitochondria and the endoplasmic reticulum, perform specialized functions essential for the cell's operation. This complexity allows for greater specialization and compartmentalization in cellular processes.