IPv4 Embedded IPv6 Unicast

[The Dark One]

Experts,
Junos accepts the following notation, very handy sometimes; do you know the exact official name for this kind of notation:

unit 0 {
    family inet {
        address 10.10.20.34/24;
    }
    family inet6 {
        address 2001:1111:2222:3333::10.10.20.34/64;
    }
}

Thanks!