The Queen and the Duke of Edinburgh have visited Cornwall in their first trip to the county since the Golden Jubilee tour in 2002.
Thousands of well-wishers greeted the Queen at the Eden Project
They toured the Eden Project biomes in St Austell before the Queen officially opened its new education building.
The Queen also unveiled plaques at Mountford House care home in Truro and the University College Falmouth and the University of Exeter Tremough campus.
Eden opened early to allow 4,000 people to visit and see the royal couple.
Engineers reduced the usual 80%-90% humidity in the 180ft-high Humid Tropics biome for the day to make it more comfortable for the Queen.
Don Murray, the curator of the biome, said the royal visitors did not appear to find it too hot.
"I think they were simply overwhelmed by the size," he said.
After admiring the hundreds of plants and mature trees in the biomes - which starred in a James Bond movie - the royal couple opened the education building, The Core.
The Core will be home to Eden's schools programme, as well as exhibitions and events.
Funded mainly by the Millennium Commission, the centre has been built on the principle of the way plants grow, with a trunk and canopy roof.
The royal couple saw a room where an 80-tonne sculpture called The Seed, fashioned from a lump of Cornish granite by artist Peter Randall-Page, will be lowered in September.
The Queen presented a personal message which will be kept in a time capsule to be buried under the sculpture.
The message said: "I am confident the Eden Project will continue to encourage a better understanding of the planet on which we live and offer a vision of hope for the future, and inspire us all to work to make this world a better place for everyone."
The Queen and Prince Philip later visited the £130m Combined Universities in Cornwall campus at Tremough, near Penryn.
They were greeted by a crowd of about 500 people and they viewed exhibitions of work by students before the Queen unveiled a plaque to mark the visit.