  This report describes the conceptual steps in reaching the design of the
AWAKE experiment currently under construction at CERN. We start with an
introduction to plasma wakefield acceleration and the motivation for using
proton drivers. We then describe the self-modulation instability --- a key to
an early realization of the concept. This is then followed by the historical
development of the experimental design, where the critical issues that arose
and their solutions are described. We conclude with the design of the
experiment as it is being realized at CERN and some words on the future
outlook. A summary of the AWAKE design and construction status as presented in
this conference is given in [1].
