Sequence diagrams are an essential tool for representing how different entities interact over time within a process. Using Mermaid.js, you can easily create sequence diagrams that visualize the flow of messages between participants, making it clear how a system or workflow operates. The core elements of Mermaid sequence diagrams include participants, messages, and activation bars. Participants are the entities involved in the process, such as users, systems, or services. Messages represent communication between these participants, and activation bars show when a participant is active during the interaction.

The syntax for Mermaid sequence diagrams is straightforward. You begin with the sequenceDiagram keyword, followed by lines that define participants using the participant keyword. Messages between participants use arrows such as ->>, -->>, or --x to indicate direction and type of communication. You can also use the activate and deactivate keywords to display activation bars, highlighting when a participant is actively involved in the process. Customization options include renaming participants, changing arrow styles, and adding notes to clarify steps or provide additional context. With these features, you can tailor your sequence diagrams to clearly illustrate any interaction or workflow.