The TARDIS has a very specific smell. I'm sure the smell has been collected from all over the universe – particles picked up over the Doctor's various travels have all landed there, so the TARDIS can smell like Earth, Raxacoricofallapatorius, New Earth, New New Earth, and Gallifrey all at the same time. Add in all of the other hundreds of planets and galaxies the Doctor has visited and you get the most unique, wonderful smell in the entire universe.

I'm in the TARDIS, leaning on the console, just taking in that smell. The Doctor is there too. His hair is wet (even Time Lords need showers) and he is running around, pushing buttons, turning dials and pulling levers. I don't even realize what we're talking about – we're just talking. There's also quite a lot of smiling and laughing. That's how it usually was with the Doctor.

I jerk awake.

It was all that one word. Was. That was my life with the Doctor. That was how the TARDIS smelled.

I roll over, and he is there. It is him, and it is not him, and I love him, and I don't. He looks the same. His face will never change again, except with age. We have a TARDIS. I don't know how he managed to get it, but he did. But it is not the TARDIS. It is not my TARDIS. The smell is different, the sheets are scratchier, and the library is quieter.

I watch him sleeping. I always wonder if he ever actually sleeps. The Doctor hardly ever slept – a few minutes each night and he was fine. Is this Doctor actually sleeping, or is he just pretending for my sake? Which side in him is more powerful – human or Time Lord?

One heart, I silently remind myself. He only has one heart. That means he should be more human. He still has all of the Doctor's memories, all of his knowledge, but he's cheekier. That would be the Donna in him. He's snappier and more controlling, but also funnier. To an outsider, I would doubt it would be very noticeable. My mum and dad, they both think he's exactly the same. But I know better.

He stirs slightly. He must have felt my eyes on him, but he doesn't wake. I look up at the ceiling, and in front of my eyes it disappears. The millions of suns and nebulas and galaxies all spread out before me. And for a moment, I think I see him. The Doctor in the TARDIS with Rose Tyler.

I wake the next morning to the sound of bare feet stepping carefully and quietly across the floor. He comes up behind me and kisses me on the cheek. "Good morning, love!" He exclaims, far too loudly for the early morning. I roll over and kiss him on the mouth anyway. His hands are hidden behind his back. He whips them around, revealing a jagged piece of metal, shining a hundred different colors.

"For my Rose," he says, smiling with pride. I sit up and take it from him, moving it around in my hands. The early morning sunlight coming in from a few, high round windows shines off it magnificently.

"What is it?" I ask, marveling. "Where is it from?"

"I picked it off the TARDIS just this morning. It's from right here." He says, gesturing wildly around him.

I look at him with a stare that I know is quite blank. "This grew off the TARDIS?" I ask, unbelieving.

"Of course it did! Come with me." He grabs my hand, pulls me out of bed, and runs out of the room, dragging me in tow. That is one thing that will always be the same for the Doctor – for him, running is the only way to get around on legs. Leading me up and down flights of stairs, through doors, around rooms and finally, to a room I had never been before, he stops abruptly. The lights are off, but he switches them on with a snap of his fingers.

The sight is unbelievable. The small piece of metal he had given me was nothing compared to what was in this room. It was full of magnificent formations of the stuff, in a hundred more colors. I walk up and touch a piece. It giggles. I turn to look at him. "It giggled." I say.

"It giggled," he replies, smiling. I look at the place where the formation meets the floor and walls of the room. Exactly as he said, it was growing out of the TARDIS. I wonder vaguely if it has roots.

"How does it grow?"

"On its exterior, the TARDIS collects dust and particles from the Vortex and all over the universe. They stick to the outside, but she doesn't maintain her shiny police box appearance by collecting intergalactic barnacles. Instead, she integrates them into her structure and they come up here." He looks around, smiling and quite obviously very pleased with himself and his machine.

"This is amazing," I say, quietly, taking in the sight. As I am looking, my nose picks up a subtle hint. It is here – the smell of the TARDIS. I turn to him, and right there, me in my pajamas, and he in his blue suit and cocky smile, I kiss him. I kiss him with such ferocity that I am, for a moment, reminded of that first kiss on Bald Wolf Bay. After he told me the three words that I needed most. I love you.

I look down at my hands, still unbelieving at their appearance. Has it really been that long ago since I was young? Since I could run and run around the universe with the Doctor and never get tired? Even my teeth feel frail. I never expected that of old age. I look over at him, sitting next to me. The Time Lord part of him knows that getting old is wrong, but he is a charming old man. He still wears those blue suits. He smiles at me, and grasps my wrinkled hand in his own.

"Remember in the early days, when I brought you here?" he reminisces, gesturing at the TARDIS growth in the room around him. "They were just saplings then, weren't they?" He is right. The jagged, multicolored, shimmering rocks have grown immensely in the time that has passed. I even have an inkling that the room had grown to fit it all, but I am not certain. I glance over at him, the man that I have spent my life with - the man that I love.

"Yes," I reply. "And we were just saplings too."