Mosquitoes are one of the most intensely studied creatures on the planet. Their role in disease transmission and nuisance biting makes them worthy of such attention. There are over 3,500 species of mosquito on Earth and they are found on every continent except Antarctica. Yet, from this great diversity, only a small handful can carry the pathogens that cause disease and it is these species which have been studied most intensely. For the purposes of public health, this substantial body of research has helped us to understand mosquito-borne disease transmission and informed the development of mosquito- and disease-control methods. But parallel to this, a fascinating and complex biology has been revealed, showing the mosquito’s incredible and unusual behavioural, anatomical and physiological traits. This chapter will explore some of the unique aspects of mosquito biology and ecology, drawn from the ever-growing body of research on the most medically important species, and highlight the sophisticated adaptations of mosquitoes to their ecological niche.