What do you think was the first form of life?
It's pretty clear that all the organisms living today, even the simplest ones, are removed from some initial life form by four billion years or so, so one has to imagine that the first forms of life would have been much, much simpler than anything that we see around us. But they must have had that fundamental property of being able to grow and reproduce and be subject to Darwinian evolution.
So it might be that the earliest things that actually fit that definition were little strands of nucleic acids. Not DNA yet—that's a more sophisticated molecule—but something that could catalyze some chemical reactions, something that had the blueprint for its own reproduction.
Would it be something we would recognize under a microscope as living, or would it be totally different?
That's a good question. I can imagine that there was a time before there was life on Earth, and then clearly there was a time X-hundred thousand years or a million years later when there were things that we would all recognize as biological. But there's no question that we must have gone through some intermediate stage where, had you been there watching them, you might have placed your bets either way.
So I can imagine that on a primordial Earth you would have replicating molecules—not particularly lifelike in our definition, but they're really getting the machinery going. Then some of them start interacting together and pretty soon you have something a little more lifelike, and then it incorporates maybe another piece of nucleic acid from somewhere else, and by the accumulation of these disparate strands of information and activity, something that you and I would look at and agree "that's biological" would have emerged.
In a nutshell, what is the process? How does life form?
The short answer is we don't really know how life originated on this planet...