diff --git a/README.md b/README.md
index 5b4237c..fdbc700 100644
--- a/README.md
+++ b/README.md
@@ -91,7 +91,10 @@ This is not a trivial task. There are almost certainly a great many complex edge
 The example below is aspirational. It isn't yet implemented - it exists in the name of [README driven development](http://tom.preston-werner.com/2010/08/23/readme-driven-development.html).
 
 ```js
-rollup.rollup( 'app.js', {
+rollup.rollup({
+  // The bundle's starting point
+  entry: 'app.js',
+
   // Override the default path resolution
   resolvePath: function ( importee, importer ) {
     // return a string or a falsy value - if falsy,
diff --git a/bin/runRollup.js b/bin/runRollup.js
index e33ef4c..585c1fc 100644
--- a/bin/runRollup.js
+++ b/bin/runRollup.js
@@ -33,13 +33,16 @@ function bundle ( options, method ) {
 		handleError({ code: 'MISSING_INPUT_OPTION' });
 	}
 
-	return rollup.rollup( options.input ).then( function ( bundle ) {
+	return rollup.rollup({
+		entry: options.input
+	}).then( function ( bundle ) {
 		var generateOptions = {
+			dest: options.output,
 			format: options.format
 		};
 
 		if ( options.output ) {
-			return bundle.write( options.output, generateOptions );
+			return bundle.write( generateOptions );
 		}
 
 		if ( options.sourcemap && options.sourcemap !== 'inline' ) {
diff --git a/gobblefile.js b/gobblefile.js
index cda2c18..fe4cde5 100644
--- a/gobblefile.js
+++ b/gobblefile.js
@@ -1,6 +1,6 @@
 var gobble = require( 'gobble' );
 
-var selfhost = 1;
+var selfhost = 0;
 
 module.exports = selfhost ?
 	gobble( 'src' )
diff --git a/src/Bundle.js b/src/Bundle.js
index 151f2a4..db13779 100644
--- a/src/Bundle.js
+++ b/src/Bundle.js
@@ -6,7 +6,9 @@ import Module from './Module';
 import ExternalModule from './ExternalModule';
 import finalisers from './finalisers/index';
 import makeLegalIdentifier from './utils/makeLegalIdentifier';
+import ensureArray from './utils/ensureArray';
 import { defaultResolver } from './utils/resolvePath';
+import { defaultLoader } from './utils/load';
 
 function badExports ( option, keys ) {
 	throw new Error( `'${option}' was specified for options.exports, but entry module has following exports: ${keys.join(', ')}` );
@@ -18,6 +20,15 @@ export default class Bundle {
 		this.base = dirname( this.entryPath );
 
 		this.resolvePath = options.resolvePath || defaultResolver;
+		this.load = options.load || defaultLoader;
+
+		this.resolvePathOptions = {
+			external: ensureArray( options.external )
+		};
+
+		this.loadOptions = {
+			transform: ensureArray( options.transform )
+		};
 
 		this.entryModule = null;
 		this.modulePromises = {};
@@ -28,7 +39,7 @@ export default class Bundle {
 	}
 
 	fetchModule ( importee, importer ) {
-		return Promise.resolve( importer === null ? importee : this.resolvePath( importee, importer ) )
+		return Promise.resolve( importer === null ? importee : this.resolvePath( importee, importer, this.resolvePathOptions ) )
 			.then( path => {
 				if ( !path ) {
 					// external module
@@ -42,7 +53,7 @@ export default class Bundle {
 				}
 
 				if ( !has( this.modulePromises, path ) ) {
-					this.modulePromises[ path ] = readFile( path, { encoding: 'utf-8' })
+					this.modulePromises[ path ] = Promise.resolve( this.load( path, this.loadOptions ) )
 						.then( source => {
 							const module = new Module({
 								path,
diff --git a/src/rollup.js b/src/rollup.js
index d182df3..09baf6f 100644
--- a/src/rollup.js
+++ b/src/rollup.js
@@ -5,16 +5,21 @@ import Bundle from './Bundle';
 let SOURCEMAPPING_URL = 'sourceMa';
 SOURCEMAPPING_URL += 'ppingURL';
 
-export function rollup ( entry, options = {} ) {
-	const bundle = new Bundle({
-		entry,
-		resolvePath: options.resolvePath
-	});
+export function rollup ( options ) {
+	if ( !options || !options.entry ) {
+		throw new Error( 'You must supply options.entry to rollup' );
+	}
+
+	const bundle = new Bundle( options );
 
 	return bundle.build().then( () => {
 		return {
 			generate: options => bundle.generate( options ),
-			write: ( dest, options = {} ) => {
+			write: options => {
+				if ( !options || !options.dest ) {
+					throw new Error( 'You must supply options.dest to bundle.write' );
+				}
+
 				let { code, map } = bundle.generate({
 					dest,
 					format: options.format,
diff --git a/src/utils/ensureArray.js b/src/utils/ensureArray.js
new file mode 100644
index 0000000..2669345
--- /dev/null
+++ b/src/utils/ensureArray.js
@@ -0,0 +1,5 @@
+export default function ensureArray ( thing ) {
+	if ( Array.isArray( thing ) ) return thing;
+	if ( thing == undefined ) return [];
+	return [ thing ];
+}
diff --git a/src/utils/load.js b/src/utils/load.js
new file mode 100644
index 0000000..1d8d826
--- /dev/null
+++ b/src/utils/load.js
@@ -0,0 +1,6 @@
+import { readFileSync } from 'sander';
+
+export function defaultLoader ( path, options ) {
+	// TODO support plugins and transformers?
+	return readFileSync( path, { encoding: 'utf-8' });
+}
diff --git a/src/utils/resolvePath.js b/src/utils/resolvePath.js
index 4b07512..08de65d 100644
--- a/src/utils/resolvePath.js
+++ b/src/utils/resolvePath.js
@@ -1,11 +1,22 @@
 import { dirname, isAbsolute, resolve } from 'path';
 
-export function defaultResolver ( importee, importer ) {
+export function defaultResolver ( importee, importer, options ) {
 	// absolute paths are left untouched
 	if ( isAbsolute( importee ) ) return importee;
 
-	// external modules stay external
-	if ( importee[0] !== '.' ) return false;
+	// we try to resolve external modules
+	if ( importee[0] !== '.' ) {
+		// unless we want to keep it external, that is
+		if ( ~options.external.indexOf( importee ) ) return null;
+
+		return resolveExternal( importee, importer, options );
+	}
 
 	return resolve( dirname( importer ), importee ).replace( /\.js$/, '' ) + '.js';
-}
\ No newline at end of file
+}
+
+function resolveExternal ( id, importer, options ) {
+	// for now, only node_modules is supported, and only jsnext:main
+
+	throw new Error( "TODO" );
+}
diff --git a/test/function/allows-external-modules-from-nested-module/_config.js b/test/function/allows-external-modules-from-nested-module/_config.js
index 918a11a..d0c980e 100644
--- a/test/function/allows-external-modules-from-nested-module/_config.js
+++ b/test/function/allows-external-modules-from-nested-module/_config.js
@@ -1,3 +1,6 @@
 module.exports = {
-	description: 'imports external modules from nested internal modules'
+	description: 'imports external modules from nested internal modules',
+	options: {
+		external: [ 'path' ]
+	}
 };
diff --git a/test/function/import-default-from-external/_config.js b/test/function/import-default-from-external/_config.js
index d2d3885..98651b7 100644
--- a/test/function/import-default-from-external/_config.js
+++ b/test/function/import-default-from-external/_config.js
@@ -1,3 +1,6 @@
 module.exports = {
-	description: 'imports default from external module'
-};
\ No newline at end of file
+	description: 'imports default from external module',
+	options: {
+		external: [ 'path' ]
+	}
+};
diff --git a/test/function/import-named-from-external/_config.js b/test/function/import-named-from-external/_config.js
index 243412e..cab932b 100644
--- a/test/function/import-named-from-external/_config.js
+++ b/test/function/import-named-from-external/_config.js
@@ -1,3 +1,6 @@
 module.exports = {
-	description: 'imports names from an external module'
-};
\ No newline at end of file
+	description: 'imports names from an external module',
+	options: {
+		external: [ 'path' ]
+	}
+};
diff --git a/test/function/import-namespace-from-external-module-renamed/_config.js b/test/function/import-namespace-from-external-module-renamed/_config.js
index 86394b3..4cb00de 100644
--- a/test/function/import-namespace-from-external-module-renamed/_config.js
+++ b/test/function/import-namespace-from-external-module-renamed/_config.js
@@ -1,3 +1,6 @@
 module.exports = {
-	description: 'imports a namespace from an external module and renames it'
+	description: 'imports a namespace from an external module and renames it',
+	options: {
+		external: [ 'path' ]
+	}
 };
diff --git a/test/function/import-namespace-from-external-module/_config.js b/test/function/import-namespace-from-external-module/_config.js
index f107139..3704e5c 100644
--- a/test/function/import-namespace-from-external-module/_config.js
+++ b/test/function/import-namespace-from-external-module/_config.js
@@ -1,3 +1,6 @@
 module.exports = {
-	description: 'imports a namespace from an external module'
-};
\ No newline at end of file
+	description: 'imports a namespace from an external module',
+	options: {
+		external: [ 'path' ]
+	}
+};
diff --git a/test/function/imports-are-deconflicted-b/_config.js b/test/function/imports-are-deconflicted-b/_config.js
index a7c1041..eceba93 100644
--- a/test/function/imports-are-deconflicted-b/_config.js
+++ b/test/function/imports-are-deconflicted-b/_config.js
@@ -1,3 +1,6 @@
 module.exports = {
-	description: 'deconflicts imports (redux)'
+	description: 'deconflicts imports (redux)',
+	options: {
+		external: [ 'path' ]
+	}
 };
diff --git a/test/function/imports-are-deconflicted/_config.js b/test/function/imports-are-deconflicted/_config.js
index 49dbfd8..345f6b8 100644
--- a/test/function/imports-are-deconflicted/_config.js
+++ b/test/function/imports-are-deconflicted/_config.js
@@ -1,3 +1,6 @@
 module.exports = {
-	description: 'deconflicts imports'
+	description: 'deconflicts imports',
+	options: {
+		external: [ 'path' ]
+	}
 };
diff --git a/test/function/shadowed-external-export/_config.js b/test/function/shadowed-external-export/_config.js
index b39af37..2a744dc 100644
--- a/test/function/shadowed-external-export/_config.js
+++ b/test/function/shadowed-external-export/_config.js
@@ -1,3 +1,6 @@
 module.exports = {
-	description: 'external modules are not shadowed'
+	description: 'external modules are not shadowed',
+	options: {
+		external: [ 'path' ]
+	}
 };
diff --git a/test/test.js b/test/test.js
index 11ef072..5f71f6e 100644
--- a/test/test.js
+++ b/test/test.js
@@ -54,7 +54,11 @@ describe( 'rollup', function () {
 			}
 
 			( config.skip ? it.skip : config.solo ? it.only : it )( dir, function () {
-				return rollup.rollup( FUNCTION + '/' + dir + '/main.js', extend( {}, config.options ) )
+				var options = extend( {}, config.options, {
+					entry: FUNCTION + '/' + dir + '/main.js'
+				})
+
+				return rollup.rollup( options )
 					.then( function ( bundle ) {
 						var unintendedError;
 
@@ -142,7 +146,11 @@ describe( 'rollup', function () {
 					config = { description: dir };
 				}
 
-				var bundlePromise = rollup.rollup( FORM + '/' + dir + '/main.js', extend( {}, config.options ) );
+				var options = extend( {}, config.options, {
+					entry: FORM + '/' + dir + '/main.js'
+				});
+
+				var bundlePromise = rollup.rollup( options );
 
 				PROFILES.forEach( function ( profile ) {
 					( config.skip ? it.skip : config.solo ? it.only : it )( 'generates ' + profile.format, function () {
@@ -172,7 +180,11 @@ describe( 'rollup', function () {
 			describe( dir, function () {
 				var config = require( SOURCEMAPS + '/' + dir + '/_config' );
 
-				var bundlePromise = rollup.rollup( SOURCEMAPS + '/' + dir + '/main.js', extend( {}, config.options ) );
+				var options = extend( {}, config.options, {
+					entry: SOURCEMAPS + '/' + dir + '/main.js'
+				});
+
+				var bundlePromise = rollup.rollup( options );
 
 				PROFILES.forEach( function ( profile ) {
 					( config.skip ? it.skip : config.solo ? it.only : it )( 'generates ' + profile.format, function () {