How to make react-datepicker display properly?

I cannot make the component react-datepicker display properly.

it actually displays like this.

I wish it could display at least like the documentation for the component does.

I first thought it was a dependency problem, and added all the dependencies the doc says are needed. The result is still the same.

Some stackoverflow questions talked about this and referred to a missing stylesheet. However I imported everything with npm, so that shouldn't be the problem.

My class component looks like this :

import React from "react";
import "./style.css";
import DatePicker from "react-datepicker";

class Filters extends React.Component {

  constructor(props) {
    super(props);
    this.state = {
      startDate : new Date()
    };
    this.handleStartChange = this.handleStartChange.bind(this);
  }

  handleStartChange = (date) => {
    this.setState({
      startDate : date
    })
  }


  render() {
    return (
      <div className="filters">
          <div id="filterbox">
            <p id="titre">Filtres</p>
            <DatePicker 
              selected={this.state.startDate}
              onChange={this.handleStartChange} />
          </div>
      </div>
    )
  }
}



export default Filters;

I apologize in advance if the problem is very obvious, I'm quite new to reactjs.