Algodoo

When a dream starts, some neurons transmit weird stuff to other neurons, where neurons which received the data send a memory signal to the memory center (hippocampus) for help to know what the neurons are talking about. On reaction, hippocampus sends the closest data matching to the neuron's data. When the neuron receives the data, you start imaginating blurry images as the brain tries its best to uncover what the neurons are sending.