When you send a message from one iPhone to another, it is very easy to spice it up with fireworks!
Steps

Step 1. Open your iPhone mailbox
The app icon is green with a white bubble above it.

Step 2. Click on a conversation
This will allow you to open it. If you want to start a new conversation, click on the pencil and notebook icon in the upper right corner of the screen and type in the recipient's name.
If messaging opens with a conversation that is not the one you want, first click the back arrow in the upper left corner of the screen to return to the messaging home page

Step 3. Write your message
To do this, type your text at the bottom of the screen, using your device's touchscreen.

Step 4. Click and hold the Send button
It's the blue arrow to the right of the text. This allows you to open the window containing the different effects you can add to your message.
If the send key is green, you or your recipient is using SMS messages, not Apple messaging

Step 5. Click Screen
The icon is located in the upper right corner of the screen.

Step 6. Slide the screen four times
You arrive at the fireworks page.

Step 7. Click the blue Send arrow
Your message is sent. When your recipient opens the message, they'll see fireworks igniting behind the text.
Advice
You can select other effects from the "Screen" page, for example lasers, balloons or confetti
Warnings
- Apple adds new effects regularly, so sometimes you have to swipe the screen longer before you get to the fireworks page.
- For your recipient to see the message, you need at least iOS version 10 of the iPhone.