The answers are yeast and penicillium.
Some yeasts are used in medicine, for example, some Saccharomyces species, Candida species, etc. They are used for the production of some amino acids, vitamins (C, B2), some proteins (insulin). Penicillium is used for production of antibiotics.
Marshmallows are probably so delicious because of several important factors. They are fluffy, soft, and oh-so sweet. They melt in your mouth and taste absolutely heavenly with chocolate and graham crackers. Or throw a couple in your hot chocolate. There's no wrong way to eat them and they're pretty cheap too.
Answer:
physical change should be the answer
Problem solving I believe
