"I'd like to try the pill to be a woman for 24 hours," Caleb explained.
"OK, very good," smiled Doctor Lydia. "Just tap your card, please-" Caleb did as she asked- "-and I'll escort you to the observation room."
As she got up and Caleb followed her, he asked, "What's the observation room?"
"Oh, we just use it to make sure once you take the pill that your body transforms correctly. It works fine 99.9% of the time, but we legally have to use it to ensure the subject is safe in their new form."
"Got it," replied Caleb as she opened the door to the glass chamber, handed him a small pink pill with a Venus symbol on it, and locked it.
"We advise you undress before taking the pill so there are no complications or irritation to the body as it changes," Doctor Lydia pointed out before Caleb could swallow the pill.
"Oh, sorry," Caleb replied blushing. He removed everything but his underwear, and looked at Doctor Lydia.
"Sorry, those have to come off too," she said. Caleb nodded and pulled them off too, and finally took the pill.
He quickly felt a dreamlike warmth spread through him, and his skin seemed to practically ripple as he breathed heavily, surprised by how aroused he felt from this. "Estrogen levels have begun to spike, activity in reproductive system surging," Doctor Lydia noted- not to him, but to his benefit at least.
He felt an odd sensation in his face and neck as his features reshaped and his larynx shrank, and bit his lip in surprised pleasure as his nipples seemed to enlarge and turn erect. Mammary glands emerged around them, and soft mounds of flesh formed as he developed breasts, which soon became large enough that they hung more noticeably from his chest than his cock did between his legs. "Breasts and upper body have developed healthily," he heard Doctor Lydia say.
Lower on his body, his skin turned smooth and lost much of its thick hair, and his butt and hips seemed to soften and expand. Only his penis and testicles remained masculine now, and they finally gave way to the changes. Caleb watched his shaft pull back into his body, rapidly turning smaller and smaller, and under it his balls were sucked up inside him and the mound of his scrotum tucked inwards. The experience was weird in his head too- he had always felt like a man because of having these parts, and losing them felt like letting go of the person he had been.
The centre where the scrotum had been sealed up suddenly seemed to peel open, and suddenly she felt she had a hold on the person she was becoming. It became totally entrenched as inside her, her former testicles linked up with a womb that had formed and her former penis settled into place above her vagina, forming her new clitoris.
Caleb was a bit surprised how instantaneously her new gender identity had clicked. She didn't feel any aversion to thinking of herself as a woman, even though she'd been a man just minutes ago.
"OK! The body's genotype has fully converted from XY to XX. Instead of having the body of a 21-year-old male, you have the body of a 21-year-old female. Does everything feel alright?" Doctor Lydia piped up.
"Um," Caleb replied in her new higher-pitched voice, surprised by its sound. "Uh, yeah, everything feels OK, thanks."
"Great! In that case, feel free to borrow some clothes from our cloakroom, and have a nice day!" Doctor Lydia smiled as Caleb stepped out of her chamber. "We'll see you again in 24 hours to make sure you change back alright."
Caleb walked through to the cloakroom and wondered what she'd do with her body for the next 24 hours...