Read receipts are available in direct and group chats, so you can see when others have seen your messages.
Tick indicators appear beneath each message:
One grey tick: The message has been sent.
Two grey ticks: The message has been delivered, but not yet read by all recipients.
Two blue ticks: The message has been read. On a direct message, this means the other user has read it. On a group chat, this means all members have read it.
In a group chat, you can also click the two grey ticks to see a list of which members have read the message so far.