*{
  font-family: Avenir, sans-serif; 
  font-size: 1em; 
  text-align: center;
  margin: 0px; padding: 0px; 
  box-sizing: border-box;
}
.conteneur-grid{
  display: grid;
  grid-template-columns: repeat(3,1fr);
  grid-template-rows: repeat(2,100px);
  border: 2px solid red;
  background-color: #DDD;
  margin: 10px;
}
.conteneur-grid > div{
  border: 1px dashed black;
}
.g1{background-color: #ED8;} /*Jaune*/
.g2{background-color: #4DA; height: 50px} /*Vert*/
.g3{background-color: #4AD;} /*Bleu*/
.g4{background-color: #A4D; height: 50px}/*Violet*/
.g5{background-color: #C24;}/*Rouge*/

.alignitemsstretch{align-items: stretch;}
.alignitemsstart{align-items: start;}
.alignitemscenter{align-items: center;}