This is the first time LEGO KidsFest has come to the Bay Area, and all three days are sold out. It's part fun, but it also part learning in workshops put on by master builders.
At last count, there are over 400 million Lego bricks in existence. Lego sets have been around 81 years, and it's what you can make with them that continues to capture the imagination of kids and inspires them to build things.
One of those kids grew up to be Chris Steininger. At age 30, he's one of seven master builders at Lego who makes these life-size figures and cars.
"The most difficult part of building a model like this is all the different colors," he said. "It makes the model look really dynamic and cool-looking, but all the different colors mean that you have to have a ton of different trays around you -- Lego brick. So when we do models, the fewer the colors the faster it builds."
The prime age for playing with LEGO bricks is about five to 12, but there are no restrictions. So a person of any age could get into it.
Some lego sets have as few as 77 pieces, but London's Tower Bridge set has 4295 pieces.
Dan Steininger got hooked on Lego while playing with his son. Now he's also a master builder.
"There's something satisfying about putting something down, snapping it together," he said. "There's something inside our brain that says, 'Oh, that's good. We have control over that. I made that.'"