Bacterial-infections are mostly due to bacteria in an adhering, biofilm-mode of growth and not due to planktonically growing, suspended-bacteria. Biofilm-bacteria are much more recalcitrant to conventional antimicrobials than planktonic-bacteria due to (1) emergence of new properties of biofilm-bacteria that cannot be predicted on the basis of planktonic properties, (2) low penetration and accumulation of antimicrobials in a biofilm, (3) disabling of antimicrobials due to acidic and anaerobic conditions prevailing in a biofilm, and (4) enzymatic modification or inactivation of antimicrobials by biofilm inhabitants. In recent years, new nanotechnology-based antimicrobials have been designed to kill planktonic, antibiotic-resistant bacteria, but additional requirements rather than the mere killing of suspended bacteria must be met to combat biofilm-infections. The requirements and merits of nanotechnology-based antimicrobials for the control of biofilm-infection form the focus of this Tutorial Review.