Metroid Prime/X-Ray Visor

Tallon Overworld
Once you have the Grapple Beam you can go after the X-Ray Visor or the Magma Beam next. Apparently the hint system can point you to either one at this point; perhaps it shows you the one closest to territory you've already explored. Regardless, we're going to cover the X-Ray Visor next because it's been reachable since you got the Power Bomb.

Great Tree Hall
Return to the Great Tree Hall and jump up to the ledge above the gate you opened earlier. There is a pillar with Spider Ball track spiraling around it. Make your way to the top and to the end of section of track that sticks out at the top. Drop to a lower side section and spiral up a branch pillar to the ledge above. Now go through the door here.

Life Grove Tunnel
Drop a Power Bomb to clear the boulder out of the path, then continue into a Morph Ball maze. This one has a half-pipe structure built in which closes into a loop. Start swinging around with the Boost Ball until you get enough momentum to carry you to the top of the loop. There's a weak spot there which will break open if you drop a bomb there, and if you drop through you'll have a Missile Expansion by the time you come out the bottom. Continue into the next room.

Life Grove
Drop off the ledge to find the X-Ray Visor. Like the Thermal Visor, it allows you to see objects that are invisible in normal light. But since it uses a different part of the spectrum you can see objects that are invisible in the Thermal Visor as well. Conversely, objects only visible in the Thermal Visor will usually still be invisible in X-Ray.

It appears at first glance that you're trapped in this little room, but if you switch to X-Ray you can see that there is more to it beyond the walls you can see. Drop a Power Bomb in the middle to break down most of the walls and reveal a much larger valley. (There is an endless stream of Seedlings that slowly crawls down the wall here, and they will nearly always drop Power Bomb ammo in case you're low.)

Now you can start finding a way out. Go left from the start to a large tree, then jump to the ledge next to it, and to another ledge with a Morph Ball sized groove in the wall. Follow the groove to a catwalk, then platform your way around the large tree to trigger an attack by Chozo Ghosts.

Fight these as usual, but you can use the X-Ray Visor to keep a lock on them making it somewhat easier. When the battle is over, a statue the roof of the little room breaks revealing a hole for a Morph Ball.

Start following the route beginning at the large tree again, but this time there's nothing to stop you from reaching the end which is the where the hole appeared. Jump in to find yourself on the ledge where you came in. Before going back though, there is a Chozo Artifact you can get here, see the Chozo Artifacts page for details.