Returning employees at NASA's Ames Research Center first saw a "welcome back" sign as they approached the front gate.
Then they were greeted personally by the center's associate director, Deborah Feng. She's expecting to spend the next few days easing the fears of the 2,400 furloughed people who work here.
"People are stressed," she said. "We got a lot of data about folks using our employee assistance program during the shutdown to manage stress, both financial and personal stress."
And that's going to take a toll on productivity.
Processing back pay is also a top priority at the U.S. Geological Survey in Menlo Park so its 450 employees can focus on their research.
"The first things first are the people, the staff that work here, making sure they're going to be paid on time and getting that paperwork in place," said Tom Brocher, USGS Earthquake Hazards Team Chief.
However, stress has also been put on taxpayers. The San Jose IRS office opened two hours late.
Neil Suri waited so he can pay taxes before leaving on a trip to India. But as the agency re-opens, it can't find Suri's paperwork.
"They haven't received anything and I don't know what's going on," he said. "I'm leaving the country, and I have to pay taxes. I want to pay by installment and nobody can help me." He adds that this means he ends up paying a penalty.
And Rukmi Patel, an international student at Santa Clara University, may have lost a campus job because she couldn't get a social security card. And she needs the money.
"Now I think it's delayed too much so we might not get shifts," she said.
So the federal government may be back open, but the impact is lingering.
There are, of course, two classes of employees coming back to work -- the government employees who will get back pay and the contractors who will not.