diff --git a/lib/httpx.rb b/lib/httpx.rb
index bf5c8846..1bac3213 100644
--- a/lib/httpx.rb
+++ b/lib/httpx.rb
@@ -15,5 +15,29 @@ require "httpx/response"
 require "httpx/client"
 
 module HTTPX
+  # All plugins should be stored under this module/namespace. Can register and load
+  # plugins.
+  #
+  module Plugins
+    @plugins = {}
+
+    # Loads a plugin based on a name. If the plugin hasn't been loaded, tries to load
+    # it from the load path under "httpx/plugins/" directory.
+    #
+    def self.load_plugin(name)
+      h = @plugins
+      unless (plugin = h[name])
+        require "httpx/plugins/#{name}"
+        raise "Plugin #{name} hasn't been registered" unless (plugin = h[name])
+      end
+      plugin
+    end
+
+    # Registers a plugin (+mod+) in the central store indexed by +name+.
+    #
+    def self.register_plugin(name, mod)
+      @plugins[name] = mod
+    end
+  end
 
 end
diff --git a/lib/httpx/channel.rb b/lib/httpx/channel.rb
index fb6b1a04..4af85a7a 100644
--- a/lib/httpx/channel.rb
+++ b/lib/httpx/channel.rb
@@ -30,7 +30,7 @@ module HTTPX
 
     def initialize(io, options, &on_response)
       @io = io
-      @options = HTTPX::Options.new(options)
+      @options = Options.new(options)
       @read_buffer = +""
       @write_buffer = +""
       @pending = []
diff --git a/lib/httpx/channel/http1.rb b/lib/httpx/channel/http1.rb
index 5d2913ad..a3740b3b 100644
--- a/lib/httpx/channel/http1.rb
+++ b/lib/httpx/channel/http1.rb
@@ -61,7 +61,8 @@ module HTTPX
 
     def on_headers_complete(h)
       log { "headers received" }
-      response = Response.new(@selector, @parser.status_code, h)
+      headers = @options.headers_class.new(h)
+      response = @options.response_class.new(@selector, @parser.status_code, headers)
       @responses << response
       request = @requests[@responses.size - 1]
       emit(:response, request, response)
diff --git a/lib/httpx/channel/http2.rb b/lib/httpx/channel/http2.rb
index c389bcff..65057f6c 100644
--- a/lib/httpx/channel/http2.rb
+++ b/lib/httpx/channel/http2.rb
@@ -45,9 +45,10 @@ module HTTPX
       end
       # stream.on(:half_close)
       # stream.on(:altsvc)
-      stream.on(:headers) do |headers|
-        _, status = headers.shift
-        response = Response.new(@selector, status, headers)
+      stream.on(:headers) do |h|
+        _, status = h.shift
+        headers = @options.headers_class.new(h)
+        response = @options.response_class.new(@selector, status, headers)
         @streams[stream.id] = response
         emit(:response, request, response)
       end
diff --git a/lib/httpx/client.rb b/lib/httpx/client.rb
index 73491df6..e3dd41b6 100644
--- a/lib/httpx/client.rb
+++ b/lib/httpx/client.rb
@@ -3,7 +3,7 @@
 module HTTPX
   class Client
     def initialize(**options)
-      @default_options = Options.new(options) 
+      @default_options = self.class.default_options.merge(options) 
       @connection = Connection.new(@default_options)
     end
 
@@ -12,7 +12,7 @@ module HTTPX
     end
 
     def request(verb, uri, **options)
-      Request.new(verb, uri, **@default_options.merge(options))
+      @default_options.request_class.new(verb, uri, **@default_options.merge(options))
     end
 
     def send(*requests)
@@ -30,5 +30,32 @@ module HTTPX
       end
       requests.size == 1 ? responses.first : responses
     end
+
+    @default_options = Options.new
+
+    class << self
+      attr_reader :default_options
+
+      def inherited(klass)
+        super
+        klass.instance_variable_set(:@default_options, @default_options.dup)
+      end
+
+      def plugin(pl, *args, &block)
+        # raise Error, "Cannot add a plugin to a frozen config" if frozen?
+        pl = Plugins.load_plugin(pl) if pl.is_a?(Symbol)
+        pl.load_dependencies(self, *args, &block) if pl.respond_to?(:load_dependencies)
+        include(pl::InstanceMethods) if defined?(pl::InstanceMethods)
+        extend(pl::ClassMethods) if defined?(pl::ClassMethods)
+        default_options.request_class.send(:include, pl::RequestMethods) if defined?(pl::RequestMethods)
+        default_options.request_class.extend(pl::RequestClassMethods) if defined?(pl::RequestClassMethods)
+        default_options.response_class.send(:include, pl::ResponseMethods) if defined?(pl::ResponseMethods)
+        default_options.response_class.extend(pl::ResponseClassMethods) if defined?(pl::ResponseClassMethods)
+        default_options.headers_class.send(:include, pl::HeadersMethods) if defined?(pl::HeadersMethods)
+        default_options.headers_class.extend(pl::HeadersClassMethods) if defined?(pl::HeadersClassMethods)
+        pl.configure(self, *args, &block) if pl.respond_to?(:configure)
+        nil
+      end
+    end
   end
 end
diff --git a/lib/httpx/options.rb b/lib/httpx/options.rb
index b92dee34..1af28886 100644
--- a/lib/httpx/options.rb
+++ b/lib/httpx/options.rb
@@ -32,13 +32,16 @@ module HTTPX
 
     def initialize(options = {})
       defaults = {
-        :proxy              => {},
-        :ssl                => {},
-        :timeout            => Timeout.by(:null), 
-        :headers            => {},
-        :cookies            => {},
-        :max_concurrent_requests => MAX_CONCURRENT_REQUESTS,
-        :max_retries        => MAX_RETRIES,
+        :proxy                    => {},
+        :ssl                      => {},
+        :timeout                  => Timeout.by(:null), 
+        :headers                  => {},
+        :cookies                  => {},
+        :max_concurrent_requests  => MAX_CONCURRENT_REQUESTS,
+        :max_retries              => MAX_RETRIES,
+        :request_class            => Class.new(Request),
+        :response_class           => Class.new(Response),
+        :headers_class            => Class.new(Headers),
       }
 
       defaults.merge!(options)
@@ -70,6 +73,7 @@ module HTTPX
     %w[
       params form json body
       proxy follow ssl max_retries
+      request_class response_class headers_class
     ].each do |method_name|
       def_option(method_name)
     end
diff --git a/lib/httpx/request.rb b/lib/httpx/request.rb
index aae7e30a..28d4f2d9 100644
--- a/lib/httpx/request.rb
+++ b/lib/httpx/request.rb
@@ -36,7 +36,7 @@ module HTTPX
 
       raise(Error, "unknown method: #{verb}") unless METHODS.include?(@verb)
 
-      @headers = Headers.new(@options.headers)
+      @headers = @options.headers_class.new(@options.headers)
       @headers["user-agent"] ||= USER_AGENT
       @headers["accept"]     ||= "*/*" 
       
@@ -55,7 +55,7 @@ module HTTPX
     end
 
     def <<(data)
-      (@body ||= +"") << data
+      @body << data
     end
 
     def authority