Mohammad,
toc, toc-expandable, toc-selective-expandable, toc-tabbed-internal-nav and toc-tabbed-external-nav
Advanced Search for one that interests you such as toc-selective-expandable and you will find it in the shadow $:/core/macros/toc
Open $:/core/macros/toc in edit mode and you can see how it works
```
\define toc-selective-expandable(tag,sort:"",itemClassFilter,exclude,path)
<$vars tag="""$tag$""" sort="""$sort$""" itemClassFilter="""$itemClassFilter$""" excluded="""$exclude$ -[[$tag$]]""" path="""$path$/$tag$""">
<ol class="tc-toc toc-selective-expandable">
<$list filter="""[all[shadows+tiddlers]tag[$tag$]!has[draft.of]$sort$] -[[$tag$]] $exclude$""">
<$list filter="[all[current]toc-link[no]]" variable="ignore" emptyMessage=<<toc-selective-expandable-empty-message>> >
<$macrocall $name=toc-unlinked-selective-expandable-body tag="""$tag$""" sort="""$sort$""" itemClassFilter="""$itemClassFilter$""" exclude=<<excluded>> path=<<path>> >
</$list>
</$list>
</ol>
</$vars>
\end
```
;Which you work through carefully and you find it "calls" `<<toc-selective-expandable-empty-message>>` If there is nothing to process which then calls toc-linked-selective-expandable-body
;Or the above calls toc-unlinked-selective-expandable-body if there is some thing
```
\define toc-linked-selective-expandable-body(tag,sort:"",itemClassFilter:" ",exclude,path)
<$set name="toc-state" value=<<qualify """$:/state/toc$path$-$(currentTiddler)$""">>>
<$set name="toc-item-class" filter="""$itemClassFilter$""" emptyValue="toc-item" value="toc-item-selected" >
<li class=<<toc-item-class>>>
<$link>
<$list filter="[all[current]tagging[]limit[1]]" variable="ignore" emptyMessage="<$button class='tc-btn-invisible'>{{$:/core/images/blank}}</$button>">
<$reveal type="nomatch" state=<<toc-state>> text="open">
<$button set=<<toc-state>> setTo="open" class="tc-btn-invisible tc-popup-keep">
{{$:/core/images/right-arrow}}
</$button>
</$reveal>
<$reveal type="match" state=<<toc-state>> text="open">
<$button set=<<toc-state>> setTo="close" class="tc-btn-invisible tc-popup-keep">
{{$:/core/images/down-arrow}}
</$button>
</$reveal>
</$list>
<<toc-caption>>
</$link>
<$reveal type="match" state=<<toc-state>> text="open">
<$macrocall $name="toc-selective-expandable" tag=<<currentTiddler>> sort="""$sort$""" itemClassFilter="""$itemClassFilter$""" exclude="""$exclude$""" path="""$path$"""/>
</$reveal>
</li>
</$set>
</$set>
\end
```
;Now notice how this in turn calls toc-selective-expandable!
;toc-unlinked-selective-expandable-body
```
\define toc-unlinked-selective-expandable-body(tag,sort:"",itemClassFilter:" ",exclude,path)
<$set name="toc-state" value=<<qualify """$:/state/toc$path$-$(currentTiddler)$""">>>
<$set name="toc-item-class" filter="""$itemClassFilter$""" emptyValue="toc-item" value="toc-item-selected">
<li class=<<toc-item-class>>>
<$list filter="[all[current]tagging[]limit[1]]" variable="ignore" emptyMessage="<$button class='tc-btn-invisible'>{{$:/core/images/blank}}</$button> <$view field='caption'><$view field='title'/></$view>">
<$reveal type="nomatch" state=<<toc-state>> text="open">
<$button set=<<toc-state>> setTo="open" class="tc-btn-invisible tc-popup-keep">
{{$:/core/images/right-arrow}}
<<toc-caption>>
</$button>
</$reveal>
<$reveal type="match" state=<<toc-state>> text="open">
<$button set=<<toc-state>> setTo="close" class="tc-btn-invisible tc-popup-keep">
{{$:/core/images/down-arrow}}
<<toc-caption>>
</$button>
</$reveal>
</$list>
<$reveal type="match" state=<<toc-state>> text="open">
<$macrocall $name="""toc-selective-expandable""" tag=<<currentTiddler>> sort="""$sort$""" itemClassFilter="""$itemClassFilter$""" exclude="""$exclude$""" path="""$path$"""/>
</$reveal>
</li>
</$set>
</$set>
\end
```
Now notice how this in turn calls toc-selective-expandable!
So lets make this simpler
toc-selective-expandable > toc-linked-selective-expandable-body (Via empty) > Calls the first macro "toc-selective-expandable"
Or
> toc-unlinked-selective-expandable-body > Calls the first macro "toc-selective-expandable"
So the first macro is repeatedly called until very part of the Tree is visited.
Regards
Tony