I don't know what I ever did before I discovered the greatness of mason jars. If you do not have these in your life 100%, you are not living. Using one every now and then doesn't count; these things are so great.
We chop up our lettuce and stuff it in mason jars. One stuffed-to-the-max jar makes a perfect size dinner salad. It also keeps FOREVER. I think the longest I've gone before eating my lettuce was 2 weeks. 2 WEEKS!!!!!!!!!! Granted, it was starting to be a little wilty, but 2 weeks in the fridge should have turned it from pink to brown to DEAD. When I have jars full of lettuce in the fridge, its easy for me to just grab it and go in the morning...perfect, simple lunch.
Way back when I made crepes for breakfast, I sliced up my strawberries and bananas the night before. Bananas....sorta like avocados and apples, they turn brown FAST. Well this picture was the day after, and look how NOT brown they are! They stayed fresh in there for a few days, actually. It was fantastic. No more brown 'nanas!
You have no idea how fun it is to drink out of a mason jar until you've actually tried it.
I made a batch of my mom's salsa and canned it. It was perfect because I could share with everyone. You want some salsa?...here, have a jar. AMAZING. And this is embarrassing, but yes its 9:43 AM and I just successfully ate half a jar of salsa. Told you it was good!