The PIENU experiment at TRIUMF is conceived for measuring the
$R = \Gamma(\pi^+\rightarrow e^+\nu + \pi^+\rightarrow e^+\nu\gamma)/
\Gamma(\pi^+\rightarrow \mu^+\nu + \pi^+\rightarrow \mu^+\nu\gamma)$
branching ratio at the <0.1\% precision level,
providing a stringent test of the electron-muon universality hypothesis.
The violation of universality can point towards the existence of new physics.