"Ok, there I go" you start. "I want to have a body of a normal, healthy, young human female, except half the size. I don't want to just be shorter. I want the body to be in exact same proportions as it would be in full-size, but with everything halved in size. The only thing not halved in size should be my vagina and the production of the hormones responsible for physical arousal. This way I want to guarantee that I won't be able to resist letting men fuck me even though in my mind I'm a straight male."
"Are you sure this is what you want?" Tanya looks at you puzzled. "An average height of a woman in USA is 5'4''. That will make you only 2 feet and 8 inches tall. That's only as tall as an average three-year old!"
"Yes, I am sure." you answer.
"Ok" she says. "Please give me a second."
Tanya walks over to a panel and a display in the wall. She presses some buttons, types some things and after a couple of minutes of that something falls down into the dispenser nearby, also sticking out of the wall.
She picks it up and hands it to you.
"This pill will realize your wish." She says. "Once you take it, the nanobots contained in it will transform you into the description you gave me in approximately half an hour."
Your eyes get big as you hear "half an hour". You anxious to see the results you already popped the pill! And your house is at least a quarter hour walk from where you are.