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Exoplanet discoveries over the past three decades have revealed an astonishing diversity of planetary systems. While significant strides have been made in understanding the population of close-in planets that dominate survey discoveries to date, we do not have a firm grasp of what other systems look like at wider separations, where our own solar system planets reside. This will change in the near future when NASA’s Roman mission undertakes a micro-lensing census of the low-mass planet population beyond ~1 AU. In this talk, I will describe how planetary dynamics theory can be applied to interpret micro-lensing planet detections. In particular, dynamics theory can link together the population statistics of bound and free-floating planets to give a comprehensive picture of how orbital evolution shapes the outer regions of planetary systems. Applied to the current results of ground-based micro-lensing surveys, I will show that this theory predicts a substantial population of “detached” Neptune-sized planets orbiting at hundreds of AU on highly eccentric orbits. The dynamical evolution that emplaces detached Neptunes on their extreme orbits doesn’t only reshape the outer regions of planetary systems; it can have dramatic system-wide consequences as well.