The discovery of the recA gene toward the middle of the 20th century sparked work in perhaps one of the most biochemically and biophysically intriguing systems of DNA repair-homologous recombination. The inner workings of this system, in particular those of the more complex eukaryotes, have been and in many ways remain mysterious. Yet at the turn of this century, a wealth of structural and genetic results has unveiled a detailed picture of the roles, relationships, and mechanics of interacting homologous recombination proteins. Here we focus on the predominant questions addressed by these exciting 21st century structural results-from detection of broken DNA ends to coordination of pathway progression. The emerging structural view of double-strand break repair, therefore, reveals the molecular basis both for functions specific to DNA recombination and for general features characterizing DNA repair processes.