Investigators seek to determine if a mobile health based intervention can be developed to target increases in childhood sleep duration.

Investigators seek to determine if an online based intervention can be developed to target increases in childhood sleep. The primary objectives of this study are to determine if different messaging strategies lead to the longer sleep duration.Children aged 9-12 who sleep about 6-8.5 hours per night will wear a Fitbit for 11 weeks in order to measure sleep patterns. Participants will have a sleep goal to meet each night. Participants will be randomized to one of thirty-two study conditions and receive text and/or email messaging. Some study arms receive additional messaging with different content and frequency of delivery. The study involves one visit to the Children's Hospital of Philadelphia (CHOP).

Inclusion Criteria:

1. Males or females age 9 to 12 years.
2. Speak, read and write in English.
3. Parental/guardian permission (informed consent) and child assent.
4. Have a computer or a tablet computer with access to the Internet, or own a smartphone with a data and text plan.
5. Parent reported time in bed on school nights between 6.0-8.5 hours in bed at night (e.g. 7-hour time in bed: go to bed at 11pm & get out of bed at 6am).

Exclusion Criteria:

1. Any clinically diagnosed sleep disorder (e.g. sleep apnea).
2. Diagnosed with a psychiatric disorder [e.g. attention deficit hyperactivity disorder (ADHD), depression, anxiety].
3. Diagnosed with an eating disorder.
4. Musculoskeletal or neurological disorder that limits physical movement and activity.
5. Use of medications (prescription or otherwise) known to affect body weight and/or sleep.