Editor's note: This story was originally published in February and has been republished with updates.
Today, everyone respects Arunachalam Muruganantham, 52, a social entrepreneur who lives in the city of Coimbatore in South India. But there was a time, he says, when his neighbors were convinced he had lost his mind. Some even believed that he was a vampire.
"It all started because I wanted to create a good sanitary napkin for my wife," he laughs.