Do you want to know an easy way to remember the 5 largest blocs of Unreached People Groups?  It’s as easy as looking at your thumb. In fact, looking at your thumb is the way to remember. Use the acrostic: T-H-U-M-B

• Tribals
• Hindu
• Unreached Chinese
• Muslim
• Buddhist

A people group is considered unreached when less than 2% of its population are Evangelical Christians.  Perhaps the best resource for learning about all Unreached People Groups, and details about each people, is from Joshua Project.