Virtually everyone has taken antibiotics. They can be lifesavers -- and they can be useless. What are they? How are they used? And what happens as the effectiveness of antibiotics continues to decline? This examines the personal and societal implications of our planet's most important -- and frequently misused -- medications. In a question-and-answer format, it unpacks the most complicated aspects of this issue, including: How antibiotics are used (and overused) in humans, plants, and livestock; the causes and consequences of bacterial resistance to antibiotics; how the globalized world enables antibiotic resistance to spread quickly; and the difficult decisions ahead for both medical care and the food system.