tesla.css

div{
    background-color: #cccccc;
}

tesla.html

<template>
    <div >
        This is Tesla Component -  {log} 
    </div>
    <br /> 
     <c-model3 onmodelclick={modelClick}></c-model3>
</template>

tesla.js

import { LightningElement, track } from 'lwc';
export default class Child1 extends LightningElement {
    @track  log = ''; 
    modelClick(e){
        this.log = this.log + ' Captured event - '+ e.detail+' ';
         const event = new CustomEvent('modelclick', {
            // detail contains only primitives
            detail: 'Event Started in Tesla'
        });
        // Fire the event from model 3
        this.dispatchEvent(event);
    }
}