Ben knew full well what he wanted to use the Chronivac for first. For a long time he'd wondered what it would've been like if he had been a girl given how much he hated his boy's body. Now he could use this thing to find out! He set it up to change his gender, and positioned himself so he could get a good view of the process. He stood in front of his bedroom mirror and stripped naked, before initiating the transformation.
He felt an odd sensation as the Chronivac's transformative process raced through his body, shifting every masculine chromosome to its feminine equivalent. Before his eyes, things started to remould- most of his flab seemed to form part of new curves on his body, his skin turning smooth and soft. His thighs seemed to expand subtly, and his arms and legs and hands and feet seemed more petite. His face resculpted subtly to look more girlish, his lips puffier, his neck less wide and his larynx retracting into his throat. His hair lengthened significantly until it flowed down to his elbows, and even in his brain and thoughts things were changing- thinking of himself as 'him', a boy, felt less natural now, and his attraction to girls was starting to transfer over to guys.
The big changes came next, and sent him reeling. His chest felt weirdly sensitive, and his nipples perked up and expanded. Under them, he felt flesh sprout as his breasts developed, and stared at his decidedly unmasculine figure. Finally he saw his penis start to recede, its four inches declining to three as his balls moved up inside... her. As she watched the penis disappear before his eyes, and felt the transformation of his testicles into her ovaries inside her, she accepted her girlhood. Very soon his penis had turned into her clitoris, and his scrotum formed into her vaginal lips as an opening formed at its centre.
Beth Isserman looked at herself in amazement. The Chronivac had changed her sex perfectly by altering one detail of her existence- changing the Y chromosome on the sperm that fertilised her to an X, making her the exact same person but the opposite sex.
She smiled as she looked at herself, surprised at how much she liked the look of her new girl's body.