As time ticks down on three chocolate-themed rounds, the bakers try not to lose their tempers. Guest judge: chocolatier Jacques Torres ("Nailed It!").

The bakers rush to make winning desserts inspired by the judges' favorite holidays.

An illuminating theme -- light -- ignites the bakers' creativity in the kitchen. Guest judge: actor Irene Choi ("Insatiable").

The bakers bring their A-game in a trio of inventive, science-inspired rounds. Guest judge: actor Paris Berelc ("Alexa & Katie").

Fashion-forward challenges force the frazzled contestants to think outside the box.

The teams work to wow the judges with confections that bring the element of surprise.

Bakers who first met online attempt to re-create popular dessert trends and serve up the next big thing. Guest judge: "Candy Queen" Jackie Sorkin.

A family theme stirs fond memories for tight-knit bakers who are brothers and sisters, mothers and sons and more. Guest judge: chef Carla Hall.

Geeky science-themed challenges get the creative juices flowing -- along with oozy zombie 'blood.'

The baking teams pour buzz-worthy ingredients like coffee, honey and alcohol into amazing edible creations.

The teams wax nostalgic with extra-sweet treats inspired by popular candies.

An ocean theme sends bakers into the deep to make seascapes, aquatic creatures and salty-sweet flavors.

The contestants serve up sweets with summery flavors that evoke the great outdoors.

Married bakers who live and work together say "I do" to delicious sweets. Guest judges: husband-and-wife TV hosts Nick and Vanessa Lachey.

Sweet and salty snacks yield yummy flavors over a trio of junk food-inspired rounds. Guest judge: comedian Fortune Feimster.

From lofty nests to baking with insects, these avian-themed challenges are for the birds. Guest judge: actor and singer Naya Rivera ("Glee").

Magical cupcakes, edible illusions and levitating cakes? What sorcery is this?! Guest judge: magician Justin Willman ("Magic for Humans").

A darkly delicious blackout theme puts the bakers to the test — and the results are decadent. Guest judge: actor and musician Tyler Posey ("Teen Wolf").

Teams take a tropical vacation with bold agendas and breezy flavors. Guest judge: actor Garcelle Beauvais (“The Real Housewives of Beverly Hills”).

Breakfast-, lunch- and dinner-themed challenges determine which team is the hungriest for victory. Guest judge: celebrity cake designer Ron Ben-Israel.