I didn't understand when I bought the 6000 microgreen arugula seeds --what microgreens were! Can I let them grow bigger, to a baby arugula size, or will they just be all leggy?

I assume they can't reseed themselves either?

I feel so silly, but I really wanted them to self-seed. I like arugula strong and so don't really care about that part. But I don't want to have to seed every week or so.

Please educate me.