Some of them are going to do wonders in our own life time,hopefully.Nanobots could flow through our blood stream, detect the cancer cells and destroy them. They may also repair the diseased cells. Suppose our cells of one of our organs fail and if they can be repaired on time the Organ will function again without any problem. Scientists may be able to work on many organs in the future like the Pancreas, Kidneys, liver etc., An onboard computer can do the work instead of the physical tools and the computer can analyse the problems and deploy chemical reagents to help the cell to heal itself.
A drop of blood can be analysed instantly the level of blood sugar, check the Pathogens and also analyse the DNA. The computer can advise you about your diet and also to tell you if you have any life-threatening disease which can be treated and cured in time before it becomes fatal. A nanobot could do the surgery without leaving any scars since it can enter and exit the body through a hypodermic needle. It can do the surgery with precision on a very small scale of less than the size of a human cell. !!
In future it is also going to be possible hopefully, a nanobot could do cosmetic surgery which may be like changing eye colour, nose or ear shape. That can be done by rearranging the atoms and molecules any part of your body that you cared to change according to what you like to do.
There are also many more applications of nanotechnology in different phases of our life and let all hope that they will all be done for the benefit of man and the society.