As the Stone Age covers around 99% of our human technological history, it would seem there is a lot to talk about when looking at the development of tools in this period. Despite our reliance on the sometimes scarce archaeological record, this is definitely the case.
The Stone Age indicates the large swathe of time during which stone was widely used to make implements. So far, the first stone tools have been dated to roughly 2,6 million years ago. The end is set at the first use of bronze, which did not come into play at the same time everywhere; the Near East was the first to enter the Bronze Age around 3,300 BCE. It must be recognised that stone was by no means the only material used for tools throughout this time, yet it is the most stubborn one when it comes to decaying and thus survives a bit better than the alternatives.
It is important to realise that the ways chosen to divide up the Stone Age into bite-size chunks (see below) depend on technological development, and not on chronological boundaries. Because these developments did not occur at the same time in all areas, strict date ranges are out of the question. Of course, this method has some difficulties, as the characteristics defining each stone tool culture are determined by us. As with all such artificially constructed ways of classification, they oversimplify things and leave many grey areas, for instance when it comes to transition periods. However, as long as this is kept in mind it is still a useful way of adding some sort of structure to such a hugely long period of time.
The Stone Age is conceived to consist of:
the Palaeolithic (or Old Stone Age)
the Mesolithic (or Middle Stone Age)
the Neolithic (or New Stone Age)
The Palaeolithic spans the time from the first known stone tools, dated to c. 2,6 million years ago, to the end of the last Ice Age around 12,000 years ago. It is further subdivided into the Early- or Lower Palaeolithic (c. 2,6 million years ago - c. 250,000 years ago); the Middle Palaeolithic (c. 250,000 years ago - c. 30,000 years ago); and the Late- or Upper Palaeolithic (c. 50,000/40,000 - c. 10,000 years ago; some of these cultures persisted into the time when the Northern Hemisphere began warming up again). Furthermore, within these frameworks, various stone cultures are identified, some of which you will find below.
The Mesolithic saw humans adapt to the warmer climate, from around 12,000 BCE until the transition to agriculture, which happened at different times in different regions, the earliest of which was around 9,000 BCE in the Near East (which due to its lightning speed sort of skipped the Mesolithic altogether). At the other extreme, farming took until around 4,000 BCE to spread all the way to Northern Europe.
The Neolithic, then, has no clear chronological starting point either, but is defined by the move to a more settled way of life based on farming and herding. The introduction of bronze marks the end of the Neolithic, which gradually happened in various areas from around 3,300 BCE onward.