Of all the islands, Chios was my other favorite (along with colorful Symi). We saw the beautiful parts of Chios, though learned later that on the day we had arrived, three boats of Syrian refugees had arrived too (Chios being just 11 km from Turkey), which is really heartbreaking. There was so much frustration apparently over dwindling food supplies and no clear path forward for assimilation that one of the refugees set fire to a refugee camp the day after we had left. We had no idea of the camps, being insulated inside the island in these charming villages.
Chios is known for two things: 1) it's the nautical training center of Greece, its hills dotted with captains' mansions, and 2) it's the only place in the world that produces mastic.
We visited a mastic grove, where the mastic is produced and gathered. Though these trees can grow elsewhere, this is the only island on the planet with conditions that allow the tree to produce mastic. It's somewhat of a mystery why.