From the slight smile on Yefreannys Isamar Muñoz López's face, it might be a surprise to learn that she is working on math equations with her dad. The photo was made after they had trekked hundreds of miles from Venezuela to the United States-Mexico border, awaiting their immigration appointment.

Yefreannys is one of many girls photojournalist Danielle Villasana has met over the last decade as she's traveled the globe, capturing images that show how girls and young women persist in spite of the issues and inequalities they face.

Villasana remembers: "She was just so happy, so full of joy, not complaining, not upset."

It's a picture that resonates on October 11 – the International Day of the Girl on the United Nations calendar of special days. Dedicating a day to girls, according to the

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