Fennel flowers in tempura from Ferran Adrià’s El Bulli.

For years, so-called molecular gastronomy, an avant-garde culinary movement best known for its gels and emulsions and its wild chemical experiments with food, has teased the palates of diners.

With Spain’s Ferran Adrià — often regarded as the founding father of the movement — announcing recently he will shut down his restaurant El Bulli in 2012 for a couple of years to revisit his approach to cooking, the state of molecular cuisine is once again brought to the forefront. To be sure, Mr. Adrià isn’t closing down the restaurant for lack of demand. El Bulli continues to receive more than one million requests for its 8,000 reservations annually; all bookings for the year are snatched up in one day in mid-October when reservations are opened.