Gene expression refers to the fundamental process by which genetic
information is read out to produce functional molecules such as
proteins. Gene expression is intrinsically noisy due to low copy numbers 
of the molecules involved. Recent experimental progress in the field of
biological imaging of single cells has shed light on the different
sources of noise in gene expression and has spurred corresponding
theoretical efforts. In this talk, I will discuss the phenomenology of
noise in gene expression and discuss the use of semiclassical methods
to describe the statistics of rare events.