Two of the main features found in the brains of people with of Alzheimer's disease, are "neurobrillary tangles" ('tangles' for short), which are made up of a "protein" called "tau", and "senile plaques" (which are made mostly from another protein called "beta-amyloid", they are also sometimes called "beta-amyloid bundles" or 'bundles' for short). The tau proteins that form the tangles previously held together a structure inside the neurons called a "microtubule" which is an important part of the neuron; it forms part of the "cytoskeleton" (cell skeleton) which is what maintains a cell's shape, and microtubules plays a part in cell communication.