 Transdermal drug delivery has several benefits such as improved patient compliance, sustained release, avoidance of gastric irritation, and elimination of the pre-systemic first-pass effect. However, only a limited number of medications can be delivered in therapeutic amounts via the transdermal route. Microneedles have been developed to enhance transdermal drug delivery, with various designs and fabrication methods available. Hydrogen-forming microneedles are particularly promising, as they create continuous conduits between dermal microcirculation and an attached patch type reservoir. Several microneedles have already been approved by regulatory agencies for clinical use, while others are still under development. Concerns and challenges associated with microneedle use are discussed. This article was authored by Kevin Eda.