When the bidding starts with three bids all under 1NT (such as 1♣-1♦-1♠), the XYZ convention can be used:
Responder can bid:
2♣ - a transfer to 2♦. This may then be passed. Other continuations are invitational.
2♦ - this is artificial and game-forcing
Higher bids are natural and game-invitational
Try it out for yourself in this quiz.