anchor.diff:              | Block.Props props -> { result with Props = props }
               | Block.IsActive state -> { result with IsActive = state }
               | Block.CustomClass customClass -> { result with CustomClass = Some customClass }
  +            | Block.Modifiers modifiers -> { result with Modifiers = modifiers |> parseModifiers }
   
           let opts = options |> List.fold parseOptions Block.Options.Empty
  -        let classes = Helpers.classes Classes.Block.Container [opts.CustomClass] [Classes.Block.State.IsActive, opts.IsActive]
  +        let classes = Helpers.classes Classes.Block.Container (opts.CustomClass::opts.Modifiers) [Classes.Block.State.IsActive, opts.IsActive]
           label (classes::opts.Props) children
   
       /// Generate <nav class="panel"></nav>
       let panel (options: GenericOption list) children =
           let opts = genericParse options
  -        let classes = Helpers.classes Classes.Container [opts.CustomClass] []
  +        let classes = Helpers.classes Classes.Container (opts.CustomClass::opts.Modifiers) []
           nav (classes::opts.Props) children
   
       /// Generate <div class="panel-heading"></div>
       let heading (options: GenericOption list) children =
           let opts = genericParse options
  -        let classes = Helpers.classes Classes.Heading [opts.CustomClass] []
  +        let classes = Helpers.classes Classes.Heading (opts.CustomClass::opts.Modifiers) []
           div (classes::opts.Props) children
   
       /// Generate <div class="panel-tabs"></div>
       let tabs (options: GenericOption list) children =
           let opts = genericParse options
  -        let classes = Helpers.classes Classes.Tabs.Container [opts.CustomClass] []
  +        let classes = Helpers.classes Classes.Tabs.Container (opts.CustomClass::opts.Modifiers) []
           div (classes::opts.Props) children
   
       /// Generate <a></a>
  
positive.code:             | Block.Props props -> { result with Props = props }
              | Block.IsActive state -> { result with IsActive = state }
              | Block.CustomClass customClass -> { result with CustomClass = Some customClass }
  
  
          let opts = options |> List.fold parseOptions Block.Options.Empty
          let classes = Helpers.classes Classes.Block.Container [opts.CustomClass] [Classes.Block.State.IsActive, opts.IsActive]
          div (classes::opts.Props) children
  
      /// Generate <label class="panel-block"></label>
  
negative.code:             /// Add `is-active` class if true
              | IsActive of bool
              | CustomClass of string
              | Modifiers of IModifier list
  
          type internal Options =
              { Props : IHTMLProp list
                CustomClass : string option
                IsActive : bool
                Modifiers : string option list }
  
              static member Empty =
                  { Props = []
                    CustomClass = None
                    IsActive = false
                    Modifiers = [] }
  
      /// Generate <div class="panel-block"></div>
      let block (options : Block.Option list) children =
  