Answer: Scabies mites (Sarcoptes scabiei)
Note that the specimen shown appears to have 6 legs, indicating that it is a nymph. Like all other acari (inc. ticks and mites), the adult will have 8 legs.
I like this case in that you can clearly see the features of the developing nymph inside the egg.
You can also appreciate the short stumpy legs terminating in spines.