Spazer Beam Search

Walkthrough: We begin Area 4 on the search for the Spazer Beam. After getting off the Elevator, run until you reach the next Chozo Seal. From there, head left and use your Grapple Beam to swing to the open platform. After defeating oncoming enemies, use the Spider Ball to scale up to the next level. Enter the first room you find, the same that holds the first Save Station of this area.

Head down by Bombing the floor, and activate the Teleportation Statue you come to. Reach the bottom of the room and pass the door to the right. Continue heading left and then hop across the platforms to reach a door that requires a missile shot to open. Inside said room is the Spazer Beam, an attack that works similarly to the Wave Beam except it shoots out three projectiles. Exit the room through the door above, and then return to the room that had the Save Station.

Missile Expansion: Inside the room with poisonous flora is a hidden missile block in the center of the room. This will be difficult to hit as you probably are having troubles shoot a missile in the very small hole that's holding the block. When the enemy below pops up from the ground, try freezing it and using them as a platform to stand on. Jump from there and shoot the hole when you pass over it, revealing the Missile Expansion.