As you ride back up the lift to Brinstar, another cutscene will play depicting Ridley piloting a massive Space Pirate ship in outer space. Now what could that be about? (you'll find out soon enough). Once back up in Brinstar the creepy hippo-faced statue on the right wall of the elevator's room will crumble, revealing a hidden room beyond.
Watch out for the Zoomer emerging from the opening (no, I don't think it knocked the wall down on its own), then go further inside to find a Chozo Statue awaiting you. Do the usual trick to be shown where the Hi-Jump Boots are located, deeper down in Norfair.
On your way back over to Norfair's lift, pick up Missile BR.06 in the shaft outside the lift leading down to Kraid's area. Proceed back down to Norfair and save your game before heading into the large lava cavern right next door to the Save Room. Once inside, make your way over to the right side of the room and shoot the door open. Run back as far left as you can, then dash to the right to build up the Speed Booster's charge.
You'll charge into the tall green shaft and break through a range of Speed Booster blocks set in the floor. Descend the shaft a little way down and head left through the first door you'll find. Clear out the enemies in this long corridor and use the space to build up the Speed Booster's charge again as you dash back into the shaft. Back in the shaft you'll break through another floor of Speed Booster blocks.
If you check your map now, you'll find that the Hi-Jump Boots aren't far off. Descend the shaft until you see a door opposite a Missile, then go inside. Cross the adjacent corridor (watch out for enemies) and blow open the red door to find the Hi-Jump Boots waiting snugly inside. Now Samus can jump much higher than normal, plus you'll be able to Spring Jump while in Morph Ball mode. Backtrack to the tall green shaft and jump over the tall wall to reach Missile NO.06.
Continue on downward as far as you can. You'll descend down past three doors, don't worry about the one at the bottom for now, as a Kiru Giru blocks your progress in the corridor beyond. Climb up to the door above and go inside to find a tall shaft home to the next Chozo Statue. Jump on to be shown where the Varia Suit resides, high up in Brinstar's northern expanse.
Exit the room via the upper door, then within the small alcove you'll find yourself in of the tall shaft, walk over to the right wall to discover a hidden Morph Ball Launcher. Use it to break through the Speed Booster block-lined floors above and to ultimately escape from this shaft. For now backtrack and return to Brinstar. On your way up to the Varia Suit's room, you'll have the option of picking up Super Missile BR.01, but be warned, it'll be difficult to retrieve.
You can also pick up Missile BR.08 along the way. Either way, once you're ready ascend to the apex of the second tall shaft (the first shaft you'll enter when coming from Norfair). At the very top head right to find a familiar green corridor. Proceed right, jumping over the tall cylinders along the way (shoot the red core to raise them up). Roll through one of the several horizontal grey pipes you'll eventually find, once through you'll discover a weird purple ball blocking the path.
You can't injure the obstacle (your shots just irritate it), but you can still use a hidden tunnel up in the wall above to make it past. Within the next room you'll be close to finding the Varia Suit. Blast the Waver and shoot up in the ceiling to eventually discover a breakable section. Jump up above to find a tall shaft heading skyward. Your target is a ledge up on the left wall, but there's fake and crumbling blocks up against the wall, so you'll have to jump from the edge of the solid blocks roughly in the center of the room.
Work out where the fake blocks are by shooting downward (your shots will go straight through them) to time your jump from the last solid block, then you should easily make it thanks to the Hi-Jump Boots (but sequence breakers can still get up there without it). Shoot up through the platform above and climb up to the door while watching for Wavers. In the following corridor you'll encounter two more of the purple ball thingys blocking the path. But watch as a pack of the tiny parasites begin to swarm all over the balls, slowly destroying them.
Once both balls have been consumed, reward the parasites by laying bombs all over them before they gang up on Samus. Make your way through the acid-filled corridor by way of the complex platforms scattered about, and remember to hold A while in Morph Ball mode to continually jump whenever Samus lands on the ground. Release the next group of parasites ahead to clear out another purple ball, then penetrate the red door ahead to finally locate the Varia Suit.
Now you'll have the pleasure of wading through the acid found throughout Brinstar without taking a scratch. You'll also be able to survive the ultra-heated zones of Norfair, so we'll be heading back there again. Backtrack down to the earlier corridor you were in, and be sure to pick up Energy Tank BR.03 on your way down.