I never knew this fact, I had imagined it being like trifle, a mixture of cream, cake or something! But interestingly, when you plant a coriander seed, the plant grows fast and plentiful but it doesn't last very long. A bit like manna, it had to be gathered while it was fresh. The bible says that it tasted great according to everyone's taste, so I guess it tasted different to each and everyone who ate it. But they were to gather only so much as to what they needed and some people took more than they required and it went rotten. I think this was God making greed impossible for his people, teaching them not to be hoarding up provisions for themselves, but to rely on Him alone.
"The word 'manna' means literally, "What is it?" recalling the Israelites' first reaction to it." NIV student version