Preface to the Special Edition on Femtochemistry and “The Hamburg Conference on Femtochemistry 2015 (FEMTO12)”

This special issue is dedicated to the memory of Dr. Ahmed Zewail, the founder of the field and the public-keynote speaker of the Leuchtturm (Tower of Light) Lecture (https://www.femto12.org/leuchtturm) at FEMTO12.