Verschillende mediums en verschillende breedtes 

// X-Small devices (portrait phones, less than 576px)
// No media query for `xs` since this is the default in Bootstrap

// Small devices (landscape phones, 576px and up)
@media (min-width: 576px) { ... }

// Medium devices (tablets, 768px and up)
@media (min-width: 768px) { ... }

// Large devices (desktops, 992px and up)
@media (min-width: 992px) { ... }

// X-Large devices (large desktops, 1200px and up)
@media (min-width: 1200px) { ... }

// XX-Large devices (larger desktops, 1400px and up)
@media (min-width: 1400px) { ... }

Bekijk het voorbeeld hier en maak dit eerst na. 

/* On screens that are 992px wide or less, go from four columns to two columns */
@media screen and (max-width: 992px) {
  .column {
    width: 50%;
  }
}

/* On screens that are 600px wide or less, make the columns stack on top of each other instead of next to each other */
@media screen and (max-width: 600px) {
  .column {
    width: 100%;
  }
}

Bekijk hier een voorbeeldje. 

@media screen and (max-width: 600px) {
  .topnav a {
    float: none;
    width: 100%;
  }
}
of in flex taal
@media screen and (max-width: 600px) {
  .topnav a {
    flex-direction: column;
    width: 100%;
  }
}

Bepaamde elementen worden verborgen in de mobiele versie van je website: 

@media screen and (max-width: 600px) {
  div.example {
    display: none;
  }
}