Captain America: The First Avenger (2011), Hydra Cosmic Energy Batteries

original movie prop

As Steve Rogers infiltrates a Hydra weapons factory, he finds these glowing power cells, each containing luminous dark energy captured from the infinitely powerful Tesseract, being assembled into larger components of the doomsday Valkyrie bomber.

Aluminum, acrylic, and resin, filled with small translucent beads which appear to emit an otherworldly glow (as also depicted onscreen during Howard Stark's experiments following Cap's return).  Bright blue illumination for each cell is created by banks of concealed LEDs, powered by a large custom internal battery and activated by a discrete switch.

From Profiles In History & Marvel Studios.