ingle molecule measurements have transformed our view of biomolecules.Owing to the ability of monitoring the activity of individual molecules

we now see them as uniquely structured

fluctuating molecules that stochastically transition between frequently many substrates

as two molecules do not follow precisely the same trajectory.Indeed

it is this discovery of critical yet short-lived substrates that were often missed in ensemble measurements that has perhaps contributed most to the better understanding of biomolecular functioning resulting from single molecule experiments.In this paper

we give a review on the three major techniques of single molecule force spectroscopy

and their applications especially in biology.The single molecular study of biotin-streptavidin interactions is introduced as a successful example.The problems and prospects of the single molecule force spectroscopy are discussed

too.