After Ridley steals the last Metroid from Ceres Space Colony, Samus follows him to Zebes.

Get the Morphing Ball Ability

Go left from your ship and shoot the door to open it. In the next area, go left until you can go no farther, then go down the hole. Go all the way to the bottom and go through the door there.

Go to the right side of the room and fall downward. From the ledge where you land, keep going downward to reach the bottom of the room. Go through the door at the bottom.

This is the room where Samus fought Mother Brain in the first Metroid game. Go to the right and you will find a room with an elevator. Stand on it and press down to go down. It will take you to the Brinstar area.

When the elevator reaches the bottom, go to the left to reach the Morphing Ball. Touch it to collect it. Now you can press down twice to roll into a ball, allowing you to roll through narrow tunnels.

Get Missiles

Go to the right from where you got the Morphing Ball, then crouch and shoot the block at the bottom of the obstacle. Then press down twice to roll into a ball and go to the right. After you are out of the tunnel, you can press up to stand up again. Keep going right, past the elevator, and go through the door at the end.

Shoot the blocks in the middle of the room and go down to the bottom. Roll through the gap on the left and go through the door.

Shoot the orb that the Chozo Statue is holding, then jump onto the missiles to get them.

Leave the room with the Chozo Statue, roll through the tunnel, then shoot upward through the blocks and go to the top of the room. Press SELECT to switch to your missiles, then shoot the door on the right with five missiles to open it. Go through.

Go to the right and roll through the tunnel at the end to find a missile tank, which increases the maximum number of missiles that you can carry.

Go to the left and go through the door. Then in the room with the blocks that you shot through earlier, go through the door on the left. Then go to the left until you reach the elevator. Stand on it and press up to return to Crateria.