Search is everywhere in Microsoft 365. You can search from SharePoint, Teams, Delve, Yammer etc.

But! You cannot search for anything from everywhere!

• Search for your Teams chat messages works only in Teams.
• But from Teams you cannot search for regular (non-group) sites and public teams sites
• All descriptions are totally out of search (e.g. site description, library/list description – including Yammer groups, Teams and regular sites).
• Public Team Sites content is not searchable from Teams and Yammer

So, what are the scopes of each search entry point in Office 365 and is there an entry point you can search for everything?

Search scopes	SharePoint Search center	SharePoint home Office portal Office desktop app Delve	Teams	Bing
SharePoint content	Yes	Yes		Yes
Teams content	Yes	Yes	Yes	Yes
Teams chats		(*1)	Yes	Yes
Yammer content	Yes	Yes		Yes
Yammer chat		(*1)		Yes
User profiles	Yes	Yes
Email

Detailed:

	Scope	Out of Scope
SharePoint Search Center	– all sites content (Teams, Yammer, regular), – user profiles – OneDrive	Teams chat Yammer chat
SharePoint Landing Page	same as SharePoint Search center but Teams chats and Yammer Conversations are coming	same as SharePoint Search Center
Office.com	same as SharePoint (Teams chats and Yammer Conversations are coming after SharePoint)	same as SharePoint
Delve
Teams	Teams content Teams chat	OneDrive Yammer User Profiles regular SharePoint sites
Bing	Everything*	* except people profiles content (e.g. about me)

Seems like the only tool you can search for EVERYTHING with is Microsoft Bing:

After Microsoft add Teams chats and Yammer conversations to SharePoint landing page search scope (then to Office home page) – it’ll be the best place to search from for everything.

More on Microsoft Search vs SharePoint Search and Microsoft Search RoadMap

Microsoft Office 365 Search: Find what you need with Microsoft Search in Bing

It is possible customize Modern Microsoft Search pages with PnP Modern Search