The Inventing Room is Willy Wonka's favourite and most secret room. It holds all of his newest inventions and candy that still needs testing, examples being the Everlasting Gobstoppers, Hair Toffee, and the Three Course Dinner Chewing Gum.
The room is a gigantic laboratory filled with machines that create candy, most notably the Gum Machine. Above the room, a giant catwalk allows the Oompa-Loompas to traverse atop the machines, accessing the controls of many machines and the room as a whole.
The Inventing Room contains an array of machines, but Wonka shows the tour group 3 of them
A large tank of water has pipes depositing Everlasting Gobstoppers, with Oompa Loompas swimming in the tank collecting them. The purpose for the tank is unknown, and it's not even confirmed if the liquid in the tank is even water.
Presumably a machine is used to create Hair Toffee, but it is not shown
The Gum Machine is the most prominent machine, as it leads to Violets downfall.