We know shockingly little about many of the conveniences we rely on in modern life. The cars we drive, the trains we ride, the smartphones into which we type our most sensitive personal data - for most of us, their inner workings are pure mystery. The same goes for our birth control. Questions abound about the tiny pills - or patches, or condoms, or intrauterine devices - that we count on to prevent unwanted pregnancies. Many women obsessively Google questions about contraception, along with other reproductive health queries. Google no further. The Lily's video series, "When Used Correctly," has answers for you.—Nneka McGuire