Electronic materials exhibit diverse physical properties. When electron correlations are strong, the behavior is even richer but the theory becomes notoriously difficult. One organizing principle, which has come to prominence in recent years, is quantum criticality.

In this talk, I will introduce the basics about the subject, at the level of dimensional analysis; describe some challenging issues about quantum criticality and the progresses that have been made in understanding them; and discuss how quantum criticality can be harnessed for new physics in correlated electron systems, particularly those located at the border of magnetism. Settings that go beyond the domain of condensed matter physics will be touched upon.