What Does it Take to Make a Scientific Discovery?For most of history, humanity was helpless in the face of plagues and epidemics. A few rare people guessed that there might be such a thing as a living thing too small to see and that such mysterious things might have something to do with diseases. But it was only a guess, and for most of history, nobody believed that such creatures could exist, or that they could be powerful enough to harm human beings.This book is aimed at young adults, and it