Most nematode-trapping fungi are dependent on specific hyphal structures on or in which nematodes can be trapped mechanically or by adhesion. These structures are a prerequisite for the ability of the fungus to invade a host and are thus crucial for survival as well as virulence. The diversity of trapping structures is large and highly dependent on the environment of the fungus. Within one single species, Arthrobotrys oligospora, not only adhesive nets are formed but also so-called conidial traps, hyphal coils around hyphae of other fungi, and appressoria in the rhizosphere of agricultural crops. In this article these structures and the conditions for their development are described. Since the trapping structures influence the survival and the virulence of their producer, it is important that we know more about the molecular background of their development and function. The application of genomics to understand the function and the development of infection structures, therefore, has substantially increased the potential of A. oligospora to become a model system for fungal morphogenesis.