There are many ways to appreciate ferns and lycophytes. We admire their shapes, from tiny, filmy ferns on tree trunks, to lacy maidenhair ferns in rock crevices, to sturdy tree ferns with their huge, dissected leaves. We wonder at the beauty of their leaves that vary from subtle shades of green to gray, pale yellow, reddish or even iridescent blue. As we become more acquainted with ferns, the fascination deepens and the questions begin. Some of the first questions are about fern habitats. How do they survive in the deep shade of forest understories? On flooded banks of streams? On wind-swept mountain tops? On hot, vertical rock faces? Why are they so abundant on tropical mountains and oceanic islands? Questions then arise about fern growth. How do they survive drought or freezing temperatures? How do they reproduce? How old are they? What is a spore and that always elusive little “gametophyte”? We also ponder how the presence of ferns impacts other organisms. Do ferns compete with seed plants? Do they get eaten by herbivores? Finally, how do humans interact with ferns? Which species are edible or have medicinal qualities? Why are some ferns a nuisance to us? What makes them weedy ferns? We, the editors of this book, have each pondered these questions, both as people who are fascinated by the beauty and variety of ferns and as scientists whose job it is to question how the natural world is assembled, collate information about it and synthesize what is known.