Part I The Context.- 1 Introduction.- 2 The Nearby Universe.- 3 The Past and the Future.- Part II Methods and Tools.- 4 Basic Techniques and their Limitations.- 5 Finding Very Distant Galaxies.- 6 Deriving Physical Parameters.- Part III Observational Results and their Interpretation.- 7 Observed Properties of High-redshift Galaxies.- 8 The Space Distribution of High-redshift Galaxies.- 9 Interactions with the Intergalactic Medium.- 10 Implications.- Part IV An Outlook to the Future.- 11 Ongoing Work.- 12 Future Facilities and their Opportunities.