I forgot to collect eggs for 3 days 
when I finally remembered I discovered one of my hens is broody and was sitting on them. when do the chicks start visibly developing? I'm scared I'll crack one open and find veins or a little heart

when I finally remembered I discovered one of my hens is broody and was sitting on them. when do the chicks start visibly developing? I'm scared I'll crack one open and find veins or a little heart