Title: What have we learnt from three years of exoplanetary helium observations?
Abstract: Because most exoplanets discovered to date are highly irradiated by their host stars, they are prone to atmospheric escape. However, until recently there had been few available methods to observe the escape in action. Around three years ago, both theoretical work and observations confirmed that the strong absorption-line triplet of metastable helium at 10830 Angstroms is a useful tracer of upper exoplanet atmospheres - which is where the escape happens. Ground-based, high-resolution spectrographs can resolve the triplet and probe the morphology and kinematics of upper exoplanet atmospheres, and plenty of capable instruments are available. Many new detections have already been made, as have many non-detections. I will discuss highlights from the first three years of exoplanetary helium observations, and present new results from NIRSPEC on Keck.