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

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").

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.

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