React Router v4

Routes.js

import React from 'react'
import Home from './Home'
import Header from './Header'
import ProjectList from './ProjectList'
import ProjectItem from './ProjectItem'
import { Route, Switch } from 'react-router-dom'

const NoMatch = () => (<div>No match!</div>)

const ProjectItemReadme = () => (<div>This is a wonderfull project!</div>)
const ProjectItemReviews = () => (<div>Here are the reviews</div>)
const ProjectItemLinks = () => (<div>Here are the links</div>)

const Routes = () => (
  <div>
    <Route component={Header} />
    <Switch>
      <Route exact path="/" component={Home} />
      <Route exact path="/projects" component={ProjectList} />
      <Route path="/projects/:id">
        <div>
          <Route component={ProjectItem} />
          <Route path="/projects/:id/readme" component={ProjectItemReadme} />
          <Route path="/projects/:id/reviews" component={ProjectItemReviews} />
          <Route path="/projects/:id/links" component={ProjectItemLinks} />
        </div>
      </Route>
      <Route component={NoMatch} />
    </Switch>
  </div>
)

export default Routes