如何让flexbox中的div出现在下一行？

<style>
    .flex-container {
        display: flex;
        flex-wrap: wrap;
    }
    .flex-item {
        width: 100px;
        height: 100px;
        margin: 10px;
        background-color: #f0f0f0;
    }
</style>

<div class="flex-container">
    <div class="flex-item"></div>
    <div class="flex-item"></div>
    <div class="flex-item"></div>
    <div class="flex-item"></div>
    <div class="flex-item"></div>
    <div class="flex-item"></div>
</div>