How to draw a participant inside another participant in a PlantUML sequence diagram?

Question

Confluence + plantuml, https://plantuml.com/sequence-diagram

@startuml
Alice -> Bob: Authentication Request
Bob --> Alice: Authentication Response

Alice -> Bob: Another authentication Request
Alice <-- Bob: Another authentication Response
@enduml

How to draw Chris inside the box of Alice pls ? So box of Alice contains box of Chris. Thx !

Answer 1

Use box,

This is the sample from the doc https://plantuml.com/sequence-diagram

@startuml

box "Internal Service" #LightBlue
    participant Bob
    participant Alice
end box
participant Other

Bob -> Alice : hello
Alice -> Other : hello

@enduml

it works for my simple case.