STUMPERS LXIV

Think of a four-letter, one-syllable word that becomes a five-letter, one-syllable word when the letter "I" is inserted into the middle of it. Both words are pronounced the same. The second word can be used to make the first word. What are the two words?

HINTS:
#1. Both words start with M.
#2. Labyrinth

Answers:

MAZE and MAIZE

(A cornfield can be made into a maze.)