Nano Machines are devices which has the property of self replications and self reassembly that is actually built from individual atoms. In the fields of Nanomachine technology, ultimate goal is to produce the Assembler which is designed to manipulate matter at the atomic level. This means that assembler will be capable of rearranging atoms from any raw materials to produce any desired products. In theory, assembler are capable of rearranging atoms of even dirts to produce potato, chair, laptops and anything else.
Another goal of nanotechnology is to embeds the property of self replication in nanomachines to produce the copies of themselves. If scientists manage to build nanomachines that can rearrange atoms, a world of exciting possibilities will open up. Especially in the fields of nanomedicine, it can provide great revolutions providing breakthrough treatments for many diseases. We can have nanomachines that can destroy targeted cells like cancerous cells providing treatments for all types of cancerous diseases. Damaged tissues and bones can be repaired using self replication phenomena and even be used to strengthen bones and muscle tissue by building molecular support structures by reassembling nearby tissue. Also we can design nanomachines that can trap viruses and destroying themselves which can be boon for patients with HIV diseases.
Nanomachines will be able to produce any desired items from any raw materials by self reassembly which can sustain the demands of burgeoning population. So, there will be no problems like starvation, no problems of clothes, houses, cars, televisions, etc. Environmental problems can also be easily tackled by releasing the swarms of nanomachines in the upper atmosphere which can destroy CFCs gases and can build up ozone gases.
Every products have pros and cons. Obviously greatest risks is associated with military application. Self replicating nanomachines designed to target and destroy organic material could be released over enemy territory reducing the population to dust within a matter of hours. Whole country can be left empty within a day by a rival country with such potential military applications.
Another serious danger of nano machines is its ability to self replicate which can make several copies of itself by rearranging the atoms of nearby matter. Even offsprings machines will be able to replicate that can leads to uncontrolled reproduction of nano machines. Furthermore, since the nanomachines are using the planet’s resources as raw material with which to replicate, the danger is that the planet could eventually be transformed into a seething mass of nanomachines.
These are all hypothetical approaches which sounds very interestings. Still we are not able to manipulate individual atoms. When technologies reaches towards extreme minituarisation and generation of the ultra-fine finishing of high quality optical components is feasible, chemists and engineers together may reach to their target for nanomachines in future if the technology is pursued with full vigor.
Ravi's Blog 
