sAve array in one custom field and access it

Hello,
I saved some data into post’s meta. this makes postmeta table a very long list. I think maybe it’s beter to group the data into one array. But seems WP automatically unpack the array into single items. Is there a way to save whole array into one custom field? If yes, how to retrive one single item from the array in this field after save?

Thanks for helping!