According to the Solar Impulse YouTube channel:
After months of preparations, the moment we've all been waiting for passed in a heartbeat! In the midst of the Bay Area rush hour traffic, the graceful solar airplane silently lifted its wings soaring high above Moffett Airfield towards the rising sun.
Piloted by Bertrand Piccard, the 6:12 am PDT (UTC-7) take off marks the launching of 2013 Across America mission and with it, the kickoff of the "Clean Generation" initiative. Solar Impulse will cross the continental United States in 5 stopovers in hopes of raising awareness about the potential of clean technologies. Thousands of Solar Impulse Supporters are already taking part in this global movement of pioneers by having their names virtually carried across the country on a USB key.
Very cool, we wish Solar Impulse godspeed in its journey!
UPDATE Saturday 3:50 pm: Here's video of the plane landing in Phoenix after completing the first leg of its journey.