I'm quite new on Material Angular and I'm trying to add some components to my project. Right now I'm trying to add the expansion-panel component example to a dialog, but the component does not work, I'm working around and I can't realize why. I'm working on Angular 5.2.0 and Material Angular 5.2.5. I already imported the module in the main.ts import {MatExpansionModule} from '@angular/material/expansion'; I created the expansion-overview.component.html <mat-accordion> <mat-expansion-panel> <mat-expansion-panel-header> <mat-panel-title> Personal data </mat-panel-title> <mat-panel-description> Type your name and age </mat-panel-description> </mat-expansion-panel-header> <mat-form-field> <input matInput placeholder="First name"> </mat-form-field> <mat-form-field> <input matInput placeholder="Age"> </mat-form-field> </mat-expansion-panel> <mat-expansion-panel (opened)="panelOpenState = true" (closed)="panelOpenState = false"> <mat-expansion-panel-header> <mat-panel-title> Self aware panel </mat-panel-title> <mat-panel-description> Currently I am {{panelOpenState ? 'open' : 'closed'}} </mat-panel-description> </mat-expansion-panel-header> <p>I'm visible because I am open</p> </mat-expansion-panel> </mat-accordion> I created the expansion-overview.component.ts import {Component} from '@angular/core'; @Component({ selector: 'jhi-expansion-overview', templateUrl: 'expansion-overview.component.html', }) export class ExpansionOverviewComponent { panelOpenState: boolean; } To finish I added the selector jhi-expansion-overview to my dialog resume <div class="modal-header"></div> <div class="modal-body"> <jhi-alert-error></jhi-alert-error> <jhi-expansion-overview></jhi-expansion-overview> </div> <div class="modal-footer"> <button type="button" class="btn custom custom-btn-secondary" data-dismiss="modal" (click)="clear()"> <span jhiTranslate="entity.action.save">Save</span> </button> <button type="button" class="btn custom custom-btn-secondary" data-dismiss="modal" (click)="clear()"> <span jhiTranslate="entity.action.cancel">Cancel</span> </button> </div> </form> In the end, I'm getting this as result: screnshot result I already use other components in my project, and this one is the only one that I'm having a problem. Does someone knows why I'm getting this result or what I'm doing wrong ? Thanks Continue reading...