Power Bomb Expansion Locations (Metroid Prime)

Power Bomb Expansion 1 (Chozo Ruins)
In the magma pool, use your grapple beam to grapple across to the other side. As soon as you land, get into morph ball mode and lay a power bomb to blow up the wall. Pick up your very first power bomb expansion.

Power Bomb Expansion 2 (Magmoor Caverns)
In the warrior shrine, use a power bomb at the base of the statue. This will create an opening. If you didn't fall in it already, go down there. Get out of morph ball mode and jump up to collect a power bomb expansion.

Power Bomb Expansion 3 (Phendrana Drifts)
In the Ice Ruins West, from the door to the courtyard entryway, jump straight across the gaps until you reach the structure with the crates on it. Shoot the ice here with your plasma beam, and then drop into the new opening to collect a power bomb expansion.

Power Bomb Expansion 4 (Phendrana Drifts)
In Phendrana's Edge, head left from the door to the upper edge tunnel. Jump across the gap to the platform. Turn right and jump across the broken bridge. Now jump to the platform on your left. From here, you'll be able to reach a grapple point to your right. Grapple from here to the next point to the left, and then to the platform against the wall ahead of you. Jump up the two floating platforms and look for another platform to jump to. Once you're up here, it's time to use the glider as a grapple point. Your goal is to get to the platform on the left side of you, so do whatever you can to make that happen. Roll through the tunnel here to get to the security cave and get your last power bomb expansion.