  A Fano resonance arises from the pathway interference between discrete and
continuum states, playing a fundamental role in many branches of physics,
chemistry and material science. Here, we introduce the concept of a
laser-assisted Fano resonance, created from two interferometric pathways that
are coupled together by an additional laser field, which introduces a
controllable phase delay between them and results in a generalized Fano
lineshape that can be actively controlled on the {\it attosecond} time scale.
Based on our experimental results of unprecedented resolution, we dynamically
image a resonant electron wave packet during its evolution directly in the time
domain, extracting both the amplitude and the phase, which allows for the
measurement of the {\it resonant} photoionization time delay. Ab-initio
calculations and simulations employing a physically transparent two-level model
agree with our experimental results, laying the groundwork for extending our
concepts into attosecond quantum control of complex systems.
