Lamb is executive director of Friends of the National Zoo, which organizes ZooLights every year. The event, which features lit animal silhouettes and musical light displays, is free and open nightly (except Monday) through Tuesday.

How did ZooLights start?

It started six years ago with looking at a way that we might bring people to the zoo at what was normally a quiet but beautiful time at the zoo. A number of zoos had tried out lighting programs, and they were quite successful. We were the first zoo to use LED lights, which are more environmentally friendly. We started out with a few LED lights, basically in animal shapes, and a few trees. Now we have a more than half a million lights along with activities -- a solar-powered carousel, snow tubing, arcade games, food and festive drinks -- and animal exhibits.

Are the animals out at night?

Some of them are inside. We open up our animal houses, and the kid's farm is open -- you can pet the animals in the barn. A number of the small mammals are nocturnal, so they're more active this time of night. The great ape house is also open, and you'll see what they do in terms of moving around and getting some sleep. It's a time most of our visitors don't get to see animals, so it's pretty special.

What's in store for ZooLights in the future?

I think it will continue to grow into a Washington tradition. We started out with just a few displays, and it's grown into an amazing event. We had 133,000 people last year. Depending on the weather, I think we stand a good chance to have 150,000 visitors, and I think that number will continue to grow. The thing that has impressed our staff so much is just how joyful people are. It lifts one's spirits.