RichText Flutter

Rich text widgets are used to display text in multiple styles within the same text area.
This way you can create different styles.
Apply different fonts, sizes, colors, etc. to different parts of the text.
The RichText widget uses a list of TextSpan widgets. Each TextSpan represents a piece of  text with a particular style.

import 'package:flutter/material.dart';

void main() {
  runApp(
      MaterialApp(
        home: Scaffold(
          body: MyApp(),
        ),
      )
  );
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return
      Center(
        child: Container(
            width: 500,
            height: 100,
            alignment: Alignment.center,
            margin: const EdgeInsets.all(20),
            child:RichText(
              text:TextSpan(
                text: "Micro",
                style: DefaultTextStyle.of(context).style,
                children: const [
                  TextSpan(
                    text: " Tutorial",
                    style: TextStyle(
                      fontWeight: FontWeight.bold,
                      color: Colors.red,
                      fontSize: 20
                    )
                  ),
                  TextSpan(
                      text: " Flutter",
                      style: TextStyle(
                          fontWeight: FontWeight.bold,
                          color: Colors.blue,
                          fontSize: 20
                      )
                  )
                ]
              ),
            )

        ),
      );
  }
}

Open Device Manager, run the emulator, and  then run the application. Next, check the working output and check the output  you declared in your code.