Bethany decided to drink from one of the yellows simply because yellow was her favorite color, not to mention the color tone of the liquid was similar to her eyes. After swallowing the liquid, Bethany noticed that it had a very particular taste, almost similar to banana porridge. On the downside, though, a bit of the liquid spilled on her clothes, but that was nothing a napkin couldn't clean up.
But before Bethany could attempt to clean herself, she began to feel a strange sensation all over her body. Eventually she noticed that something weird was starting to happen. For some reason, she was getting smaller while everything around her was getting bigger. But what astonished her the most was how her clothes changed while she continued to shrink. At one point she was dressed as a high school student only to later end up dressed as a little ballerina.
It wasn't until it was all over that she finally figured out what had just happened. It's not that she was shrinking, but rather regressing. And her clothes were actually changing according to how old she was at the moment.
Now Bethany was a 1-year-old baby girl, who was now wearing a white onesie that said "Baby Genius" and had a drawing of an atom on it. Her hair was now quite short and tied into ponytails with small white ribbons. Lastly, she was wearing a diaper and little white socks.
While this would have upset anyone, Bethany surprisingly didn't seem to mind being a baby. After all, she was already used to being transformed by different experiments so she decided to take advantage of this and see what she could do now that she was a baby again.