My daughters are toddlers now, but I'll never forget my reaction the first time someone asked me if I was excited to start them on solids: I almost cried. Up until that point, I was their only food source, and I liked that level of dependence. Plus, the closer we inched to the six-month-mark, the more I was reminded that time moves too quickly. Alas, the clock wasn't going to slow down, and my girls were guaranteed to get hungrier. But when it came to starting babies on solids, I felt lost. There are a lot of opinions on when,...