go to the first room. UP, Left, grapple to middle,up, go up middle space. keep on searching 'cause now I just forgot. Sorry I have a bad memory. By the way, the metroids here are slightly bigger than the little one. SPOILER ALERT
The little one grows big, tries to kill you, and when your fighting Mother Brain she will Hyper Beam you. when your almost dead, Little buddy will come and suck lives and the Hyper Beam from her and give it to you. then He tries to finish her off but the Mother brain KILLS him with round shot. There are other metroids in tourain, normal, mennacing size. use ice and missle