Yolk-shell　nanostructures　(YSNs)　composed　of　a　core　within　a　hollow　cavity　surrounded　by　a　porous　outer　shell　have　received　tremendous　research　interest　owing　to　their　unique　structural　features,　fascinating　physicochemical　properties,　and　widespread　potential　applications.　Here,　a　comprehensive　overview　of　the　design,　synthesis,　and　biomedical　applications　of　YSNs　is　presented.　The　synthetic　strategies　toward　YSNs　are　divided　into　four　categories,　including　hard-templating,　soft-templating,　self-templating,　and　multimethod　combination　synthesis.　For　the　hard-　or　soft-templating　strategies,　different　types　of　rigid　or　vesicle　templates　are　used　for　making　YSNs.　For　the　self-templating　strategy,　a　number　of　unconventional　synthetic　methods　without　additional　templates　are　introduced.　For　the　multimethod　combination　strategy,　various　methods　are　applied　together　to　produce　YSNs　that　cannot　be　obtained　directly　by　only　a　single　method.　The　biomedical　applications　of　YSNs　including　biosensing,　bioimaging,　drug/gene　delivery,　and　cancer　therapy　are　discussed　in　detail.　Moreover,　the　potential　superiority　of　YSNs　for　these　applications　is　also　highlighted.　Finally,　some　perspectives　on　the　future　research　and　development　of　YSNs　are　provided.