After an inspiring Opening Keynote from CNN anchor Soledad O’Brien and a chance to kick back and socialize at the Welcome Celebration on Sunday, ISTE 2015 attendees arrived Monday to get down to business.

A dizzying array of workshops, lectures, Ignite sessions, posters, snapshots, spotlights and other formats offered up topics as diverse as flipped learning, student data security, standards and Minecraft.

Most people made time to play at the playgrounds, which offered hands-on fun with robots, augmented reality and other tools.

Thousands of attendees swarmed opening day at the Expo Hall, looking for a sneak peek at the latest tools to transform learning in their classrooms. The hall also hosted the Ed Tech Start-Up Pitch Fest where a dozen companies pitched their innovative ed tech solutions. The presentations were rated by judges and the audience. Two winners in both the morning and afternoon rounds will go to the finals Tuesday.

Meanwhile, some very different presenters were sharing unique ideas at the popular EdTekTalks. Adam Braun, founder of Pencils of Promise; Annie Griffiths, photographer for National Geographic and a women’s rights activist; Sergei Lupashin, an aerial robotics researcher and inventor; Amy O'Toole, a 15-year-old scientist; and Hadi Partovi, co-founder of Code.org, shared their insights.

Check out a sampling of photos from the day’s events in the slideshow below.