Wow! I love that question. Let's chat about this for a while.

The first thing we need to figure out is the definition of a cell. Well, most scientists think of a cell is a non-random (meaning there is a pattern or purpose) collection of organic molecules surrounded by a bag, called the membrane. To answer your questions, we have to go to Western Australia. In Western Australia, there are these mounds of bacteria called stromatolite . They are really, really cool!

Not too long ago, scientists found "fossils" of single cells in these mounds, and it is clear from the radioactivity (all things have a small amount of harmless radioactivity that is great for determining the age of something) that the cells were 3.5 million years old. WOW!

Can you tell me the difference between a prokaryote and eukaryote? Which is older do you think? Good luck!

This is an important question which has both scientific, philosophical or religious implications. The answer is we do not know for sure. Let me give you a summary of what is the current scientific thinking: Carbon and hydrogen atoms were already part of the universe a few million years after it was created. That is after the "Big Bang" which is the key event from which the universe started. The atoms of Hydrogen and Carbon that were present may have been brought together through electric discharges (thunder lightnings) which were thought to be numerous at the beginning of the Earth existence. Once the hydrogen and carbon molecules formed, they assembled to form hydrocarbon molecules which are the primary components of the cells. These hydrocarbons are essential to the existence of the DNA which is the mother component of any cell nucleus. The DNA is essential to the process of cell replication. Indeed scientist have reproduced the process hydrocarbon molecule synthesis by producing electric discharges in a test tube containing hydrogen and carbon atoms!!.

As you can see my answer is long and not that simple. I am sorry but this reflects our poor knowledge of the birth of the very first cell. If you have more questions please ask me.