The LHCb collaboration has reported the first observation of the rare decay $B^+ \rightarrow \pi^+ \mu^+ \mu^-$. This decay was observed with a significance of 5.2σ using data from $pp$ collisions corresponding to an integrated luminosity of 1.0 fb$^{-1}$ collected with the LHCb detector. The measured branching fraction is $(2.3 \pm 0.6$ (stat.) $\pm 0.1$ (syst.))$\times 10^{-8}$, and the ratio of the branching fractions for $B^+ \rightarrow \pi^+ \mu^+ \mu^-$ and $B^+ \rightarrow K^+ \mu^+ \mu^-$ is measured to be $0.053 \pm 0.014$ (stat.) $\pm 0.001$ (syst.). The decay $B^+ \rightarrow \pi^+ \mu^+ \mu^-$ is sensitive to different classes of operators than the well-measured decay $B^+ \rightarrow K^+ \mu^+ \mu^-$, making it a valuable tool for studying flavor physics. The observation of this decay provides a new probe for studying the Cabibbo-Kobayashi-Maskawa matrix elements and testing flavor symmetry models.The LHCb collaboration has reported the first observation of the rare decay $B^+ \rightarrow \pi^+ \mu^+ \mu^-$. This decay was observed with a significance of 5.2σ using data from $pp$ collisions corresponding to an integrated luminosity of 1.0 fb$^{-1}$ collected with the LHCb detector. The measured branching fraction is $(2.3 \pm 0.6$ (stat.) $\pm 0.1$ (syst.))$\times 10^{-8}$, and the ratio of the branching fractions for $B^+ \rightarrow \pi^+ \mu^+ \mu^-$ and $B^+ \rightarrow K^+ \mu^+ \mu^-$ is measured to be $0.053 \pm 0.014$ (stat.) $\pm 0.001$ (syst.). The decay $B^+ \rightarrow \pi^+ \mu^+ \mu^-$ is sensitive to different classes of operators than the well-measured decay $B^+ \rightarrow K^+ \mu^+ \mu^-$, making it a valuable tool for studying flavor physics. The observation of this decay provides a new probe for studying the Cabibbo-Kobayashi-Maskawa matrix elements and testing flavor symmetry models.