“Necessity begets the invention!” This quote suits well for the Shack Hartmann sensor. In the late 1960s, Roland Shack and Ben Platt of Optical Science Center at the University of Arizona modified a Hartmann screen by replacing its apertures with an array of lenslets. They wanted to increase the quality of satellite images taken from the Earth. Since then, this method has found applications in a wide variety of settings from improving images of the vast Cosmos to the more down to earth measurements of the aberrations in human eye. This technique has become widespread throughout the world with hundreds of millions of astronomical images benefiting from the process to millions of corrective surgeries that will be performed in the upcoming years to enhance vision thanks to a convenient characterization of patient eyes for treatment of complex refractive errors.