Although you may not yet know what you want to major in, which department or program at MIT appeals to you and why? (*) (100 words or fewer)
The department of Biological Engineering appeals to me because it will satisfy my curiosity in biology and technology. Since the first day of volunteering at a research lab, I have been attracted to the field of biological engineering. The idea that my entire biological system was encoded in tiny molecules fascinated me, and the fact that, through technology, we could study these microscopic objects in a macroscopic scale excited me. The department of Biological Engineering and research programs like UROP, BioMAN, CAACB and NEWDIGS will enable me to explore my interests in life sciences and to create innovative technologies.
Some parts, like "The idea that my entire biological system was encoded in tiny molecules fascinated me," make you seem less intellectual. I suggest you try to upgrade your vocabulary a tad in a few places (e.g. "tiny molecules" maybe "convoluted braids" or "infinitismal particles").
I would also change the phrases ending with "excited me" so that the sentence isn't so redundant. I also would change "microscopic objects in a macroscopic scale" unless you plan to add something to elaborate on this (if you wanted to keep it and elaborate I would toss the rest of the sentence and start the new sentence with "I was enraptured by the idea that, through technology, we could study such microscopic objects in such a macroscopic scale, in the context of life, human knowledge, even the very fabrics of space-time!")
Do whatever feels right, and Good Luck!