GOOD QUESTION.

The short answer is: nobody knows.

There are a great many different kinds of bacteria, and those bacteria are more different from each-other and from non-bacterial life that we suspect that the common ancestor of us all was some kind of bacterium-like organism that lived more than three billion years ago. Nobody yet knows how that first living cell arose from nonliving matter. An incomplete list of hypotheses include:

1. Coacervates: the chemicals that make up cell membranes naturally form into soapy bubbles in water, and if they have the right proteins inside they can have a sort of metabolism that is in some ways life-like.

2. Zeolites: zeolites are clay minerals that can catalyze chemical reactions like enzymes can. It is possible that the first biochemistry happened on the surfaces of these mineral grains.

3. Non-cellular life: all life that we know about is composed of cells, but there are non-cellular things in nature that resemble living things, namely viruses. Moreover, we do know that proteins aren't the only things that can catalyze reactions; RNA can do that, too, and RNA is the genetic material in many viruses (HIV for example). Viruses are not organisms in the traditional sense - they require cellular machinery to reproduce - but perhaps virus-like organisms bound in proteins or other chemicals originated before cells did?

4. Meteorites from space: it has been suggested that life on Earth came from elsewhere in the universe, Mars being a particularly plausible suggestion because Mars was probably wet before the Earth was. Of course, this just raises the question of how life arose on Mars (or wherever).

Great question! Honestly, the answer is that we have no idea. The origin of life is one of science's greatest mysteries. Maybe you can become a scientist and answer this question for the rest of us! There are several theories that try to explain how life began on Earth over 3 billion years ago, however no one has ever been able to create life in a laboratory (yet) so we can not say if any of these theories are true. We do know that life started with some chemistry, but how exactly this happened is still not known.

If you check out this amazing video by PBS on "Revealing the Origins of Life", they explain some of the latest research findings and theories as to how life began:

One last thought- although it is true that we don't know how the very first organism came to life, we do know for a fact that all other living organisms arose from this common ancestor through the process of evolution.