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Stockholders’ Equity (Details Narrative) - USD ($) |  |  |  |  |  | 1 Months Ended | 3 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jan. 10, 2022 | Mar. 31, 2021 | Mar. 19, 2021 | Jan. 22, 2021 | Dec. 04, 2018 | Jan. 31, 2021 | Sep. 30, 2018 | Mar. 31, 2022 | Mar. 31, 2021 | Dec. 31, 2021 | Dec. 31, 2020 | Mar. 03, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Shelf registration statement amount |  |  | $ 100,000,000 |  |  |  | $ 75,000,000 |  |  |  |  |
Reverse stock split, description |  |  |  |  |  |  |  | On February 28, 2022, the Company effected a 15-for-1 reverse stock split of its common stock which was made effective for trading purposes as of the commencement of trading on March 1, 2022. As of that date, each 15 shares of issued and outstanding common stock and equivalents was consolidated into one share of common stock. All shares have been restated to reflect the effects of the 15-for-1 reverse stock split. In addition, at the market open on March 1, 2022, the Company’s common stock started trading under a new CUSIP number 15117N602 although the Company’s ticker symbol, CLSN, remained unchanged |  |  |  |
Stockholders equity note changes in capital structure, description |  |  |  |  |  |  |  | To continue listing on The NASDAQ Capital Market, which requires that the Company comply with the applicable listing requirements under NASDAQ Marketplace Rules, which requirements include, among others, a minimum bid price of at least $1.00 per share. On December 2, 2021, the Company received a letter from NASDAQ indicating that the closing bid price of the Company’s Common Stock fell below $1.00 per share for the previous 30 consecutive business days, and that the Company was therefore not in compliance with the minimum bid price requirement for continued inclusion on The NASDAQ Capital Market. The Company had 180 calendar days, until May 31, 2022, to regain compliance with this requirement, which occurs when the closing bid price of the Company’s Common Stock is at least $1.00 per share for a minimum of ten consecutive business days during the 180-day compliance period |  |  |  |
Reverse stock split common stock outstanding |  |  |  |  |  |  |  | 5,770,467 |  |  |  |
Common stock, shares outstanding |  |  |  |  |  |  |  | 5,770,467 |  | 5,770,516 |  |
Proceeds from issuance of common stock |  |  |  |  |  |  |  |  | $ 38,943,478 |  |  |
Share price | $ 285 |  |  |  |  |  |  |  |  |  |  |
Preferred stock, shares issued |  |  |  |  |  |  |  | 0 |  | 0 |  |
Preferred stock, par value | $ 300 |  |  |  |  |  |  | $ 0.01 |  | $ 0.01 |  |
Proceeds from issuance of preferred stock | $ 14,250,000 |  |  |  |  |  |  |  |  |  |  |
Common Stock, Par or Stated Value Per Share |  |  |  |  |  |  |  | $ 0.01 |  | $ 0.01 |  |
Proceeds from issuance under placement |  |  |  |  |  |  |  | $ 1,000,000 |  |  |  |
Preferred stock, stated value |  |  |  |  |  |  |  |  |  |  |  | $ 300
Preferred stock, shares outstanding |  |  |  |  |  |  |  | 0 |  | 0 |  |
Interest expense on preferred stock |  |  |  |  |  |  |  | $ (4,551,567) |  |  |  |
Series A Convertible Redeemable Preferred Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Share price | $ 300 |  |  |  |  |  |  |  |  |  |  |
Preferred stock, shares issued | 50,000 |  |  |  |  |  |  |  |  |  |  |
Preferred stock, par value | $ 0.01 |  |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of preferred stock | $ 28,500,000 |  |  |  |  |  |  |  |  |  |  |
Preferred stock, conversion price | $ 13.65 |  |  |  |  |  |  |  |  |  |  |
Conversion of stock, shares issued | 1,098,901 |  |  |  |  |  |  |  |  |  |  |
Common Stock, Par or Stated Value Per Share | $ 13.65 |  |  |  |  |  |  |  |  |  |  |
Preferred stock, shares outstanding |  |  |  |  |  |  |  |  |  |  |  | 50,000
Series B Convertible Redeemable Preferred Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Share price | $ 300 |  |  |  |  |  |  |  |  |  |  |
Preferred stock, shares issued | 50,000 |  |  |  |  |  |  |  |  |  |  |
Preferred stock, par value | $ 0.01 |  |  |  |  |  |  |  |  |  |  |
Preferred stock, conversion price | $ 15.00 |  |  |  |  |  |  |  |  |  |  |
Conversion of stock, shares issued | 1,000,000 |  |  |  |  |  |  |  |  |  |  |
Preferred stock, voting rights | right to cast 3,000 votes per share of Series B Preferred Stock on the Reverse Stock Split |  |  |  |  |  |  |  |  |  |  |
Common Stock, Par or Stated Value Per Share | $ 15.00 |  |  |  |  |  |  |  |  |  |  |
Preferred stock, shares outstanding |  |  |  |  |  |  |  |  |  |  |  | 50,000
Series A & B Preferred Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from issuance under placement |  |  |  |  |  |  |  | 1,110,000 |  |  |  |
Interest expense on preferred stock |  |  |  |  |  |  |  | 4,551,567 |  |  |  |
Shares issued, redemption value |  |  |  |  |  |  |  | 3,000,000 |  |  |  |
Legal fees |  |  |  |  |  |  |  | $ 441,567 |  |  |  |
Capital on DemandTM Sales Agreement [Member] |  |  |  |  |  |  |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Less than 12 months, unrealized gains, fair value |  |  |  |  | $ 16,000,000.0 |  |  |  |  |  |  |
Capital on Demand Agreement [Member] |  |  |  |  |  |  |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Shares issued, shares |  |  |  |  |  |  |  |  |  | 500,000 | 300,000 |
Proceeds from issuance of common stock |  |  |  |  |  |  |  |  |  | $ 6,900,000 | $ 6,200,000 |
Securities Purchase Agreement [Member] | January 2021 Registered Direct Offering [Member] |  |  |  |  |  |  |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Shares issued, shares |  |  |  | 1,728,395 |  |  |  |  |  |  |  |
Proceeds from issuance of common stock |  |  |  | $ 35,000,000 |  |  |  |  |  |  |  |
Share price |  |  |  | $ 20.25 |  |  |  |  |  |  |  |
Placement agent fee description |  |  |  |  |  | In connection with the January 2021 Offering, the Company entered into a placement agent agreement with A.G.P./Alliance Global Partners (“AGP,” and together with Brookline Capital Markets, the “January 2021 Placement Agents”) pursuant to which the Company agreed to pay the January 2021 Placement Agents a cash fee equal to 7% of the aggregate gross proceeds raised from the sale of the securities sold in the January 2021 Offering and reimburse the January 2021 Placement Agents for certain of their expenses in an amount not to exceed $82,500 |  |  |  |  |  |
Securities Purchase Agreement [Member] | March 2021 Registered Direct Offering [Member] |  |  |  |  |  |  |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Shares issued, shares |  | 769,230 |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of common stock |  | $ 15,000,000 |  |  |  |  |  |  |  |  |  |
Share price |  | $ 19.50 |  |  |  |  |  |  | $ 19.50 |  |  |
Placement agent fee description |  | Placement Agent Agreement”) with AGP, as lead placement agent (together with JonesTrading Institutional Services LLC and Brookline Capital Markets, a division of Arcadia Securities, LLC, serving as co-placement agents, the “March 2021 Placement Agents”), pursuant to which the Company agreed to pay the March 2021 Placement Agents an aggregate cash fee equal to 7% of the aggregate gross proceeds raised from the sale of the securities sold in the offering and reimburse the Placement Agents for certain of their expenses in an amount not to exceed $82,500 |  |  |  |  |  |  |  |  |  |
Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares outstanding |  |  |  |  |  |  |  | 6,600,000 |  |  |  |
Warrants issued |  |  |  |  |  |  |  | 2,500,000 |  |  |  |
Proceeds from issuance under placement |  |  |  |  |  |  |  | $ 110,000 |  |  |  |
Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares outstanding |  |  |  |  |  |  |  | 400,000 |  |  |  |
Warrants issued |  |  |  |  |  |  |  | 200,000 |  |  |  |
Common Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Reverse stock split common stock outstanding |  |  |  |  |  |  |  | 86,557,736 |  |  |  |
Shares issued, shares |  |  |  |  |  |  |  |  | 2,206,272 |  |  |

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- Definition Description of the reverse stock split arrangement. Also provide the retroactive effect given by the reverse split that occurs after the balance sheet date but before the release of financial statements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SAB Topic 4.C) -URI https://asc.fasb.org/extlink&oid=120397183&loc=d3e187143-122770 + Details
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