We arepleasedtopresentthesixthvolumeofProgressinUltrafastIntenseLaserS- ence. As the frontiers of ultrafast intense laser science rapidly expand ever outward, there continues to be a growing demand for an introduction to this interdisciplinary research?eldthatisatoncewidelyaccessibleandcapableofdeliveringcutting-edge developments. Our series aims to respond to this call by providing a compilation of concise review-style articles written by researchers at the forefront of this research ?eld, so that researcherswith differentbackgroundsas well as graduatestudentscan easily grasp the essential aspects. As in previousvolumesof PUILS, each chapterof this bookbeginswith an int- ductory part, in which a clear and concise overview of the topic and its signi?cance is given, and moves onto a description of the authors' most recent research results. All the chapters are peer-reviewed. The articles of this sixth volume cover a diverse rangeoftheinterdisciplinaryresearch?eld,andthetopicsmaybegroupedintothree categories: responses of molecules to ultrashort intense laser pulses (Chaps. 1 - 4), generation and characterization of attosecond pulses and high-order harmonics (Chaps. 5 - 8), and?lamentationand laser-plasma interactionand their applications (Chaps. 9 - 11).