She illustrates catcalls in the exact spots where they happened.

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Sophie Sandberg was 15 years old when she first experienced harassment on the streets of New York City. Cat-calling, winking, or wolf-whistling is an unfortunate reality many young women face daily on streets around the world, and it’s time for it to stop.

That’s why Sandberg, now a 21-year-old student at New York University, created a project called “Catcalls of NYC.” The project attempts to combat street harassment by bringing an acute awareness to it. Sandberg calls on her Instagram followers to send in the intrusive and often vulgar things street harassers have said to them. She then visits the location of the incident and writes the harasser’s exact phrases in brightly-colored chalk on the sidewalk.

“By writing the comments on the sidewalk where they happened, I raise public awareness about the issue,” Sandberg told HuffPost. “The colorful chalk and colorful words catch people’s eyes. They force those who wouldn’t normally experience catcalling to take a second look.”

The phrases range from banal remarks like “Excuse me, miss” to obscene phrases such as “Lift up your dress. Show us that pussy.” After each remark, Sandberg writes the hashtag #StopStreetHarassment, hoping it will not just bring awareness to the issue, but inspire people to step up and take action.

“I want people who feel silenced, objectified or victimized to understand that they can be agents of change,” Sandberg said. “One voice can contribute to a collective movement. With that, we have power and we cannot be silenced.”

Sixty-five percent of women in the U.S. say they have experienced street harassment, according to a 2014 poll by Stop Street Harassment. While Sandberg’s project can be difficult to look at, it demands attention. It is absolutely necessary.