Carbon　based　dots　(CDs)　composed　of　sp2　carbon　structures　and　surface　functional　groups　are　a　new　kind　of　carbon　nanomaterials,　exhibiting　unique　luminescent　properties　due　to　the　quantum　confinement　and　edge　effects.　This　chapter　introduces　CDs　in　detail　from　their　synthetic　strategies,　morphological　and　structural　characteristics,　luminescent　properties　and　mechanisms,　and　sensing　applications.　The　synthesis　methods　are　summarized　as　“top-down”　and　“bottom-up”　approaches.　Luminescent　properties　discussed　include　photoluminescence,　upconversion　luminescence,　chemiluminescence,　electrochemiluminescence.　Sensing　applications　mainly　refer　to　the　chemical　and　biological　sensors　based　on　the　luminescent　properties　of　CDs.　This　chapter　provides　an　overview　of　the　research　field　and　gives　future　perspectives　for　developing　the　exciting　materials.　©　Springer　International　Publishing　Switzerland　2016.