This paper discusses the critical necessity of teaching students about the social and ethical responsibilities of scientists. Both a university scientist and a middle school science teacher reflect on the value of teaching the ethical issues that confront scientists. In the development of the atomic bomb in the US-led Manhattan Project, scientists faced the growing threat of atomic bombs by the Germans and Japanese and the ethical issues involved in successfully completing such a destructive weapon. The Manhattan Project is a prime example of the types of ethical dilemmas and social responsibilities that scientists may confront.