The Doctor's TARDIS had a laboratory.
While staying in London, on 31 March 1963, Susan came home from school and tried to find the Doctor. She searched both his laboratory and the control room, but found him in neither. (PROSE: Time and Relative)
Amy and Tony Barker once accidentally stowed away in the TARDIS, and unintentionally locked themselves in the Doctor's laboratory. Later, the TARDIS landed on the Sense Sphere, and the First Doctor used his laboratory to synthesise prussic acid, which he then used to kill a Zilgan. Unbeknownst to the Doctor, Tony had been observing him from underneath a bench in the laboratory. (PROSE: The Monsters from Earth)
During the time the TARDIS was immobilized and everyone was acting strangely, Barbara Wright found the TARDIS laboratory. There she was assaulted by books, boxes and various bits of equipment from the benches. (PROSE: The Edge of Destruction)
The Doctor who visited Karn with Jenny Wilson and Jimmy Forbes altered one of the fragments of the Crystal of All Power in the TARDIS laboratory while it was in his possession, thereby sabotaging the Daleks' intended use of the Crystal. (AUDIO: Seven Keys to Doomsday)
When Ace was new on board the TARDIS, she explored its interiors and found the lab. She thought it was similar to Frankenstein's lab, but with better lights. Ace didn't tell the Seventh Doctor she found it, because she knew he'd lock it up to keep her from making Nitro-9. She couldn't always find the place afterwards. (PROSE: Echo)