The three overlapping revolutions are advances in Genetics, Nanotechnology and strong artificial intelligence (Robotics).
Kurzweil sees these three as being the heart of the Singularity. The biological/genetic revolution will take off first, followed by faster and even bigger advances in nanotechnology and even more so as strong artificial intelligence gets its traction. And... Ta Da!... we are now in Epoch Five when human and computer intelligences are all mixed together and much bigger and growing faster than the predecessors.
"G" comes first and it will do a whole lot. But, much like DNA evolution continues today, but it is out-classed in speed by technology evolution, G will be outclassed by the N and R successors. There is only so much change you can push through the purely biological system.
Here Kurzweil talks about his personal efforts to make his body longer lasting. (as mentioned earlier) He is hoping to last long enough to be part of the R revolution and have some of his thinking uploaded into the massive information net that the R revolution will make possible.
Before that happens, and something that will help Kurzweil in his efforts, will be the N revolution -- when nanotechnology comes to the fore.
The first big boost of nanotech is that it will bring huge efficiencies to every manufacturing process. As this revolution kicks in the threat of humans causing resource exhaustion on earth will fade away simply because all things will be made with so little cost in energy or materials. In thirty years resource exhaustion will be as worrisome as small pox is today.
The second big boost is that nanotech can also be used inside biological bodies. It can do lots and lots to make the biological body be healthier, work better and live longer. Ummm... if fiddling with genes can't fix your problem, then having thousands of sub-bacteria size robots inside you surely can! It's heady stuff to think about.
And finally, the R revolution means that thinking will become a hybrid process -- part will happen in the biologic brain, part will happen in nanobots in the brain and body, and part will happen in external nanobots and the strong AI of the world-wide communication and computational network whose existence means the Singularity has happened. Really heady stuff!
In this chapter Kurzweil goes into great detail on the tools that will become available for these revolutions and some of the first uses for them.