PIXEL is the new UI for the Pi, which will be on all new installations. To upgrade an existing Pi issue the following commands:
sudo apt-get update
sudo apt-get dist-upgrade
sudo apt-get install -y rpi-chromium-mods
sudo apt-get install -y python-sense-emu python3-sense-emu
sudo apt-get install -y python-sense-emu-doc realvnc-vnc-viewer