Mobile devices along with wearable sensors facilitate our ability to deliver supportive behavioral treatments to users anytime and anywhere. These treatments can include a wide variety of content such cognitive, behavioral, social and motivational support. These interventions are being developed and employed across a variety of health fields, including to improve medication adherence, encourage physical activity and healthier eating as well as to support recovery in addictions. Critical questions in the optimization of mobile health interventions include: "Does the user benefit from a particular type of mobile health notification or text message?" and "Does the user's current context such as location, time, mood impact the usefulness of the mobile health notification. In this talk we discuss the micro-randomized trial design and associated data analyses for use in optimizing mobile health interventions. We illustrate the ideas with the micro-randomized trials across a variety of fields.