Gantt charts are a powerful way to visualize project timelines, showing how tasks are scheduled over time and how they relate to each other. In Mermaid.js, you use a specific syntax to define each task, including its name, the dates it starts and ends, and any dependencies it might have on other tasks. Each task is written on its own line, and you can specify additional information like the section it belongs to, who is responsible, and even milestones.

To define a task in a Mermaid Gantt chart, you must include the task name and its date range. The basic structure for a Gantt chart in Mermaid is as follows:

• You start with the keyword gantt;
• Then specify the chart's title, date format, and axis format;
• After that, you list your tasks, each with a label, an optional identifier, and a start and end date;
• Dependencies are shown by linking tasks using the after keyword or by referencing task identifiers.

You can further customize Gantt charts in Mermaid.js by changing the appearance of tasks, adding milestones, and organizing your timeline into sections. To add a milestone, set a task's duration to 0d. You can also group tasks under section headings for better organization. Customizing colors and assigning resources to tasks is possible by adding parameters such as crit for critical tasks or using color attributes. This flexibility allows you to highlight important phases, deadlines, or dependencies in your project, making your timeline both informative and visually clear.