* Plasma membrane: This is a thin, flexible barrier that surrounds the cell and regulates what enters and leaves. It is composed of a phospholipid bilayer.

* Cytoplasm: The gel-like substance that fills the cell and contains the organelles.

* Ribosomes: These are small, granular structures responsible for protein synthesis.

* DNA (Deoxyribonucleic acid): The genetic material of the cell, containing instructions for building and maintaining the organism. In bacteria, this DNA is located in a region called the nucleoid. In eukaryotes, DNA is found within the nucleus.

While these are the most fundamental structures shared by all cells, there are some nuances to consider:

* Nucleus: Eukaryotic cells have a nucleus, where DNA is housed. Prokaryotic cells lack a true nucleus, instead having their DNA located in the nucleoid region.

* Organelles: Eukaryotic cells contain a variety of other membrane-bound organelles (like mitochondria, Golgi apparatus, endoplasmic reticulum) that perform specialized functions. Prokaryotes have fewer organelles, and these are generally not membrane-bound.

Let me know if you'd like more detail on any of these structures!